| 1. |
- Barsoum, Emad, 1979-, et al.
(författare)
-
{alpha}3, a transposable element that promotes host sexual reproduction
- 2010
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 24:15, s. 33-44
-
Tidskriftsartikel (refereegranskat)abstract
- Theoretical models predict that selfish DNA elements require host sex to persist in a population. Therefore, a transposon that induces sex would strongly favor its own spread. We demonstrate that a protein homologous to transposases, called alpha3, was essential for mating type switch in Kluyveromyces lactis. Mutational analysis showed that amino acids conserved among transposases were essential for its function. During switching, sequences in the 5' and 3' flanking regions of the alpha3 gene were joined, forming a DNA circle, showing that alpha3 mobilized from the genome. The sequences encompassing the alpha3 gene circle junctions in the mating type alpha (MATalpha) locus were essential for switching from MATalpha to MATa, suggesting that alpha3 mobilization was a coupled event. Switching also required a DNA-binding protein, Mating type switch 1 (Mts1), whose binding sites in MATalpha were important. Expression of Mts1 was repressed in MATa/MATalpha diploids and by nutrients, limiting switching to haploids in low-nutrient conditions. A hairpin-capped DNA double-strand break (DSB) was observed in the MATa locus in mre11 mutant strains, indicating that mating type switch was induced by MAT-specific DSBs. This study provides empirical evidence for selfish DNA promoting host sexual reproduction by mediating mating type switch.
|
|
| 2. |
- Bergsland, M, et al.
(författare)
-
Sequentially acting Sox transcription factors in neural lineage development
- 2011
-
Ingår i: Genes & development. - : Cold Spring Harbor Laboratory. - 1549-5477 .- 0890-9369. ; 25:23, s. 2453-2464
-
Tidskriftsartikel (refereegranskat)abstract
- Pluripotent embryonic stem (ES) cells can generate all cell types, but how cell lineages are initially specified and maintained during development remains largely unknown. Different classes of Sox transcription factors are expressed during neurogenesis and have been assigned important roles from early lineage specification to neuronal differentiation. Here we characterize the genome-wide binding for Sox2, Sox3, and Sox11, which have vital functions in ES cells, neural precursor cells (NPCs), and maturing neurons, respectively. The data demonstrate that Sox factor binding depends on developmental stage-specific constraints and reveal a remarkable sequential binding of Sox proteins to a common set of neural genes. Interestingly, in ES cells, Sox2 preselects for neural lineage-specific genes destined to be bound and activated by Sox3 in NPCs. In NPCs, Sox3 binds genes that are later bound and activated by Sox11 in differentiating neurons. Genes prebound by Sox proteins are associated with a bivalent chromatin signature, which is resolved into a permissive monovalent state upon binding of activating Sox factors. These data indicate that a single key transcription factor family acts sequentially to coordinate neural gene expression from the early lineage specification in pluripotent cells to later stages of neuronal development.
|
|
| 3. |
- Calvo, Charles-Félix, et al.
(författare)
-
Vascular endothelial growth factor receptor 3 directly regulates murine neurogenesis.
- 2011
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 25:8
-
Tidskriftsartikel (refereegranskat)abstract
- Neural stem cells (NSCs) are slowly dividing astrocytes that are intimately associated with capillary endothelial cells in the subventricular zone (SVZ) of the brain. Functionally, members of the vascular endothelial growth factor (VEGF) family can stimulate neurogenesis as well as angiogenesis, but it has been unclear whether they act directly via VEGF receptors (VEGFRs) expressed by neural cells, or indirectly via the release of growth factors from angiogenic capillaries. Here, we show that VEGFR-3, a receptor required for lymphangiogenesis, is expressed by NSCs and is directly required for neurogenesis. Vegfr3:YFP reporter mice show VEGFR-3 expression in multipotent NSCs, which are capable of self-renewal and are activated by the VEGFR-3 ligand VEGF-C in vitro. Overexpression of VEGF-C stimulates VEGFR-3-expressing NSCs and neurogenesis in the SVZ without affecting angiogenesis. Conversely, conditional deletion of Vegfr3 in neural cells, inducible deletion in subventricular astrocytes, and blocking of VEGFR-3 signaling with antibodies reduce SVZ neurogenesis. Therefore, VEGF-C/VEGFR-3 signaling acts directly on NSCs and regulates adult neurogenesis, opening potential approaches for treatment of neurodegenerative diseases.
|
|
| 4. |
- Cantù, Claudio, et al.
(författare)
-
Pax6-dependent, but β-catenin-independent, function of Bcl9 proteins in mouse lens development.
- 2014
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 28:17, s. 1879-84
-
Tidskriftsartikel (refereegranskat)abstract
- Bcl9 and Bcl9l (Bcl9/9l) encode Wnt signaling components that mediate the interaction between β-catenin and Pygopus (Pygo) via two evolutionarily conserved domains, HD1 and HD2, respectively. We generated mouse strains lacking these domains to probe the β-catenin-dependent and β-catenin-independent roles of Bcl9/9l and Pygo during mouse development. While lens development is critically dependent on the presence of the HD1 domain, it is not affected by the lack of the HD2 domain, indicating that Bcl9/9l act in this context in a β-catenin-independent manner. Furthermore, we uncover a new regulatory circuit in which Pax6, the master regulator of eye development, directly activates Bcl9/9l transcription.
|
|
| 5. |
- Do, DV, et al.
(författare)
-
A genetic and developmental pathway from STAT3 to the OCT4-NANOG circuit is essential for maintenance of ICM lineages in vivo
- 2013
-
Ingår i: Genes & development. - : Cold Spring Harbor Laboratory. - 1549-5477 .- 0890-9369. ; 27:12, s. 1378-1390
-
Tidskriftsartikel (refereegranskat)abstract
- Although it is known that OCT4–NANOG are required for maintenance of pluripotent cells in vitro, the upstream signals that regulate this circuit during early development in vivo have not been identified. Here we demonstrate, for the first time, signal transducers and activators of transcription 3 (STAT3)-dependent regulation of the OCT4–NANOG circuitry necessary to maintain the pluripotent inner cell mass (ICM), the source of in vitro-derived embryonic stem cells (ESCs). We show that STAT3 is highly expressed in mouse oocytes and becomes phosphorylated and translocates to the nucleus in the four-cell and later stage embryos. Using leukemia inhibitory factor (Lif)-null embryos, we found that STAT3 phosphorylation is dependent on LIF in four-cell stage embryos. In blastocysts, interleukin 6 (IL-6) acts in an autocrine fashion to ensure STAT3 phosphorylation, mediated by janus kinase 1 (JAK1), a LIF- and IL-6-dependent kinase. Using genetically engineered mouse strains to eliminate Stat3 in oocytes and embryos, we firmly establish that STAT3 is essential for maintenance of ICM lineages but not for ICM and trophectoderm formation. Indeed, STAT3 directly binds to the Oct4 and Nanog distal enhancers, modulating their expression to maintain pluripotency of mouse embryonic and induced pluripotent stem cells. These results provide a novel genetic model of cell fate determination operating through STAT3 in the preimplantation embryo and pluripotent stem cells in vivo.
|
|
| 6. |
- Fender, Aurelie, et al.
(författare)
-
RNAs actively cycle on the Sm-like protein Hfq
- 2010
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 24:23, s. 2621-2626
-
Tidskriftsartikel (refereegranskat)abstract
- Hfq, a protein required for small RNA (sRNA)-mediated regulation in bacteria, binds RNA with low-nanomolar K-d values and long half-lives of complexes (>100 min). This cannot be reconciled with the 1-2-min response time of regulation in vivo. We show that RNAs displace each other on Hfq on a short time scale by RNA concentration-driven (active) cycling. Already at submicromolar concentrations of competitor RNA, half-lives of RNA-Hfq complexes are approximate to 1 min. We propose that competitor RNA associates transiently with RNA-Hfq complexes, RNAs exchange binding sites, and one of the RNAs eventually dissociates. This solves the "strong binding-high turn-over" paradox and permits efficient use of the Hfq pool.
|
|
| 7. |
- Henriksson, S, et al.
(författare)
-
The scaffold protein WRAP53β orchestrates the ubiquitin response critical for DNA double-strand break repair
- 2014
-
Ingår i: Genes & development. - : Cold Spring Harbor Laboratory. - 1549-5477 .- 0890-9369. ; 28:24, s. 2726-2738
-
Tidskriftsartikel (refereegranskat)abstract
- The WD40 domain-containing protein WRAP53β (WD40 encoding RNA antisense to p53; also referred to as WDR79/TCAB1) controls trafficking of splicing factors and the telomerase enzyme to Cajal bodies, and its functional loss has been linked to carcinogenesis, premature aging, and neurodegeneration. Here, we identify WRAP53β as an essential regulator of DNA double-strand break (DSB) repair. WRAP53β rapidly localizes to DSBs in an ATM-, H2AX-, and MDC1-dependent manner. We show that WRAP53β targets the E3 ligase RNF8 to DNA lesions by facilitating the interaction between RNF8 and its upstream partner, MDC1, in response to DNA damage. Simultaneous binding of MDC1 and RNF8 to the highly conserved WD40 scaffold domain of WRAP53β facilitates their interaction and accumulation of RNF8 at DSBs. In this manner, WRAP53β controls proper ubiquitylation at DNA damage sites and the downstream assembly of 53BP1, BRCA1, and RAD51. Furthermore, we reveal that knockdown of WRAP53β impairs DSB repair by both homologous recombination (HR) and nonhomologous end-joining (NHEJ), causes accumulation of spontaneous DNA breaks, and delays recovery from radiation-induced cell cycle arrest. Our findings establish WRAP53β as a novel regulator of DSB repair by providing a scaffold for DNA repair factors.
|
|
| 8. |
- Ishiguro, K, et al.
(författare)
-
Meiosis-specific cohesin mediates homolog recognition in mouse spermatocytes
- 2014
-
Ingår i: Genes & development. - : Cold Spring Harbor Laboratory. - 1549-5477 .- 0890-9369. ; 28:6, s. 594-607
-
Tidskriftsartikel (refereegranskat)abstract
- During meiosis, homologous chromosome (homolog) pairing is promoted by several layers of regulation that include dynamic chromosome movement and meiotic recombination. However, the way in which homologs recognize each other remains a fundamental issue in chromosome biology. Here, we show that homolog recognition or association initiates upon entry into meiotic prophase before axis assembly and double-strand break (DSB) formation. This homolog association develops into tight pairing only during or after axis formation. Intriguingly, the ability to recognize homologs is retained in Sun1 knockout spermatocytes, in which telomere-directed chromosome movement is abolished, and this is the case even in Spo11 knockout spermatocytes, in which DSB-dependent DNA homology search is absent. Disruption of meiosis-specific cohesin RAD21L precludes the initial association of homologs as well as the subsequent pairing in spermatocytes. These findings suggest the intriguing possibility that homolog recognition is achieved primarily by searching for homology in the chromosome architecture as defined by meiosis-specific cohesin rather than in the DNA sequence itself.
|
|
| 9. |
- Johansson, Marcus JO, et al.
(författare)
-
Nonsense-mediated mRNA decay maintains translational fidelity by limiting magnesium uptake
- 2010
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 24:14, s. 1491-1495
-
Tidskriftsartikel (refereegranskat)abstract
- Inactivation of the yeast nonsense-mediated mRNA decay (NMD) pathway stabilizes nonsense mRNAs and promotes readthrough of premature translation termination codons. Although the latter phenotype is thought to reflect a direct role of NMD factors in translation termination, its mechanism is unknown. Here we show that the reduced termination efficiency of NMD-deficient cells is attributable to increased expression of the magnesium transporter Alr1p and the resulting effects of elevated Mg2+ levels on termination fidelity. Alr1p levels increase because an upstream ORF in ALR1 mRNA targets the transcript for NMD. Our results demonstrate that NMD, at least in yeast, controls Mg2+ homeostasis and, consequently, translational fidelity.
|
|
| 10. |
- Kelly, GL, et al.
(författare)
-
Targeting of MCL-1 kills MYC-driven mouse and human lymphomas even when they bear mutations in p53
- 2014
-
Ingår i: Genes & development. - : Cold Spring Harbor Laboratory. - 1549-5477 .- 0890-9369. ; 28:1, s. 58-70
-
Tidskriftsartikel (refereegranskat)abstract
- The transcriptional regulator c-MYC is abnormally overexpressed in many human cancers. Evasion from apoptosis is critical for cancer development, particularly c-MYC-driven cancers. We explored which anti-apoptotic BCL-2 family member (expressed under endogenous regulation) is essential to sustain c-MYC-driven lymphoma growth to reveal which should be targeted for cancer therapy. Remarkably, inducible Cre-mediated deletion of even a single Mcl-1 allele substantially impaired the growth of c-MYC-driven mouse lymphomas. Mutations in p53 could diminish but not obviate the dependency of c-MYC-driven mouse lymphomas on MCL-1. Importantly, targeting of MCL-1 killed c-MYC-driven human Burkitt lymphoma cells, even those bearing mutations in p53. Given that loss of one allele of Mcl-1 is well tolerated in healthy tissues, our results suggest that therapeutic targeting of MCL-1 would be an attractive therapeutic strategy for MYC-driven cancers.
|
|
| 11. |
- Ljung, Karin
(författare)
-
Linking photoreceptor excitation to changes in plant architecture
- 2012
-
Ingår i: Genes and Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 26, s. 785-790
-
Tidskriftsartikel (refereegranskat)abstract
- Plants sense neighbor proximity as a decrease in the ratio of red to far-red light, which triggers a series of developmental responses. In Arabidopsis, phytochrome B (PHYB) is the major sensor of shade, but PHYB excitation has not been linked directly to a growth response. We show that the basic helix-loop-helix (bHLH) transcription factor PIF7 (phytochrome-interacting factor 7), an interactor of PHYB, accumulates in its dephosphorylated form in shade, allowing it to bind auxin biosynthetic genes and increase their expression. New auxin synthesized through a PIF7-regulated pathway is required for shade-induced growth, linking directly the perception of a light quality signal to a rapid growth response.
|
|
| 12. |
- Malewicz, Michal, et al.
(författare)
-
Essential role for DNA-PK-mediated phosphorylation of NR4A nuclear orphan receptors in DNA double-strand break repair
- 2011
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 25:19, s. 2031-2040
-
Tidskriftsartikel (refereegranskat)abstract
- DNA-dependent protein kinase (DNA-PK) is a central regulator of DNA double-strand break (DSB) repair; however, the identity of relevant DNA-PK substrates has remained elusive. NR4A nuclear orphan receptors function as sequence-specific DNA-binding transcription factors that participate in adaptive and stress-related cell responses. We show here that NR4A proteins interact with the DNA-PK catalytic subunit and, upon exposure to DNA damage, translocate to DSB foci by a mechanism requiring the activity of poly(ADP-ribose) polymerase-1 (PARP-1). At DNA repair foci, NR4A is phosphorylated by DNA-PK and promotes DSB repair. Notably, NR4A transcriptional activity is entirely dispensable in this function, and core components of the DNA repair machinery are not transcriptionally regulated by NR4A. Instead, NR4A functions directly at DNA repair sites by a process that requires phosphorylation by DNA-PK. Furthermore, a severe combined immunodeficiency (SCID)-causing mutation in the human gene encoding the DNA-PK catalytic subunit impairs the interaction and phosphorylation of NR4A at DSBs. Thus, NR4As represent an entirely novel component of DNA damage response and are substrates of DNA-PK in the process of DSB repair.
|
|
| 13. |
- Nerusheva, Olga O., et al.
(författare)
-
Tension-dependent removal of pericentromeric shugoshin is an indicator of sister chromosome biorientation
- 2014
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory Press (CSHL). - 0890-9369 .- 1549-5477. ; 28:12, s. 1291-1309
-
Tidskriftsartikel (refereegranskat)abstract
- During mitosis and meiosis, sister chromatid cohesion resists the pulling forces of microtubules, enabling the generation of tension at kinetochores upon chromosome biorientation. How tension is read to signal the bioriented state remains unclear. Shugoshins form a pericentromeric platform that integrates multiple functions to ensure proper chromosome biorientation. Here we show that budding yeast shugoshin Sgo1 dissociates from the pericentromere reversibly in response to tension. The antagonistic activities of the kinetochore-associated Bub1 kinase and the Sgo1-bound phosphatase protein phosphatase 2A (PP2A)-Rts1 underlie a tension-dependent circuitry that enables Sgo1 removal upon sister kinetochore biorientation. Sgo1 dissociation from the pericentromere triggers dissociation of condensin and Aurora B from the centromere, thereby stabilizing the bioriented state. Conversely, forcing sister kinetochores to be under tension during meiosis I leads to premature Sgo1 removal and precocious loss of pericentromeric cohesion. Overall, we show that the pivotal role of shugoshin is to build a platform at the pericentromere that attracts activities that respond to the absence of tension between sister kinetochores. Disassembly of this platform in response to intersister kinetochore tension signals the bioriented state. Therefore, tension sensing by shugoshin is a central mechanism by which the bioriented state is read.
|
|
| 14. |
- Ning, Jue, et al.
(författare)
-
Comparative genomics in Chlamydomonas and Plasmodium identifies an ancient nuclear envelope protein family essential for sexual reproduction in protists, fungi, plants, and vertebrates
- 2013
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory Press (CSHL). - 0890-9369 .- 1549-5477. ; 27:10, s. 1198-1215
-
Tidskriftsartikel (refereegranskat)abstract
- Fertilization is a crucial yet poorly characterized event in eukaryotes. Our previous discovery that the broadly conserved protein HAP2 (GCS1) functioned in gamete membrane fusion in the unicellular green alga Chlamydomonas and the malaria pathogen Plasmodium led us to exploit the rare biological phenomenon of isogamy in Chlamydomonas in a comparative transcriptomics strategy to uncover additional conserved sexual reproduction genes. All previously identified Chlamydomonas fertilization-essential genes fell into related clusters based on their expression patterns. Out of several conserved genes in a minus gamete cluster, we focused on Cre06.g280600, an ortholog of the fertilization-related Arabidopsis GEX1. Gene disruption, cell biological, and immunolocalization studies show that CrGEX1 functions in nuclear fusion in Chlamydomonas. Moreover, CrGEX1 and its Plasmodium ortholog, PBANKA_113980, are essential for production of viable meiotic progeny in both organisms and thus for mosquito transmission of malaria. Remarkably, we discovered that the genes are members of a large, previously unrecognized family whose first-characterized member, KAR5, is essential for nuclear fusion during yeast sexual reproduction. Our comparative transcriptomics approach provides a new resource for studying sexual development and demonstrates that exploiting the data can lead to the discovery of novel biology that is conserved across distant taxa.
|
|
| 15. |
- Nyström, Thomas, 1960, et al.
(författare)
-
Peroxiredoxins, gerontogenes linking aging to genome instability and cancer
- 2012
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 26:18, s. 2001-2008
-
Tidskriftsartikel (refereegranskat)abstract
- Age is the highest risk factor known for a large number of maladies, including cancers. However, it is unclear how aging mechanistically predisposes the organism to such diseases and which gene products are the primary targets of the aging process. Recent studies suggest that peroxiredoxins, antioxidant enzymes preventing tumor development, are targets of age-related deterioration and that bolstering their activity (e.g., by caloric restriction) extends cellular life span. This review focuses on how the peroxiredoxin functions (i.e., as peroxidases, signal transducers, and molecular chaperones) fit with contemporary theories of aging and whether peroxiredoxins could be targeted therapeutically in the treatment of age-associated cancers.
|
|
| 16. |
- Park, Hyun-Sook, et al.
(författare)
-
Novel role for a bacterial nucleoid protein in translation of mRNAs with suboptimal ribosome-binding sites
- 2010
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 24:13, s. 1345-1350
-
Tidskriftsartikel (refereegranskat)abstract
- In Escherichia coli, the major nucleoid protein H-NS limits transcription by acting as a repressor or transcriptional silencer, presumably by its ability to close the looped chromosome domains in the nucleoid through DNA-protein-DNA bridging. Here, we demonstrate the direct involvement of H-NS as a positive factor stimulating translation of the malT mRNA. In vitro studies showed that H-NS facilitates a repositioning of the 30S preinitiation complex on the malT mRNA. H-NS stimulation of translation depended on the AU-rich -35 to -40 region of the mRNA. Several additional examples were found demonstrating a novel function for H-NS in translation of genes with suboptimal ribosome-binding sequences.
|
|
| 17. |
- Pogenberg, Vivian, et al.
(författare)
-
Restricted leucine zipper dimerization and specificity of DNA recognition of the melanocyte master regulator MITF
- 2012
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 1549-5477 .- 0890-9369. ; 26:23, s. 2647-2658
-
Tidskriftsartikel (refereegranskat)abstract
- Microphthalmia-associated transcription factor (MITF) is a master regulator of melanocyte development and an important oncogene in melanoma. MITF heterodimeric assembly with related basic helix-loop-helix leucine zipper transcription factors is highly restricted, and its binding profile to cognate DNA sequences is distinct. Here, we determined the crystal structure of MITF in its apo conformation and in the presence of two related DNA response elements, the E-box and M-box. In addition, we investigated mouse and human Mitf mutations to dissect the functional significance of structural features. Owing to an unusual three-residue shift in the leucine zipper register, the MITF homodimer shows a marked kink in one of the two zipper helices to allow an out-of-register assembly. Removal of this insertion relieves restricted heterodimerization by MITF and permits assembly with the transcription factor MAX. Binding of MITF to the M-box motif is mediated by an unusual nonpolar interaction by Ile212, a residue that is mutated in mice and humans with Waardenburg syndrome. As several related transcription factors have low affinity for the M-box sequence, our analysis unravels how these proteins discriminate between similar target sequences. Our data provide a rational basis for targeting MITF in the treatment of important hereditary diseases and cancer.
|
|
| 18. |
- Royo, H, et al.
(författare)
-
ATR acts stage specifically to regulate multiple aspects of mammalian meiotic silencing
- 2013
-
Ingår i: Genes & development. - : Cold Spring Harbor Laboratory. - 1549-5477 .- 0890-9369. ; 27:13, s. 1484-1494
-
Tidskriftsartikel (refereegranskat)abstract
- In mammals, homologs that fail to synapse during meiosis are transcriptionally inactivated. This process, meiotic silencing, drives inactivation of the heterologous XY bivalent in male germ cells (meiotic sex chromosome inactivation [MSCI]) and is thought to act as a meiotic surveillance mechanism. The checkpoint protein ATM and Rad3-related (ATR) localizes to unsynapsed chromosomes, but its role in the initiation and maintenance of meiotic silencing is unknown. Here we show that ATR has multiple roles in silencing. ATR first regulates HORMA (Hop1, Rev7, and Mad2) domain protein HORMAD1/2 phosphorylation and localization of breast cancer I (BRCA1) and ATR cofactors ATR-interacting peptide (ATRIP)/topoisomerase 2-binding protein 1 (TOPBP1) at unsynapsed axes. Later, it acts as an adaptor, transducing signaling at unsynapsed axes into surrounding chromatin in a manner that requires interdependence with mediator of DNA damage checkpoint 1 (MDC1) and H2AFX. Finally, ATR catalyzes histone H2AFX phosphorylation, the epigenetic event leading to gene inactivation. Using a novel genetic strategy in which MSCI is used to silence a chosen gene in pachytene, we show that ATR depletion does not disrupt the maintenance of silencing and that silencing comprises two phases: The first is dynamic and reversible, and the second is stable and irreversible. Our work identifies a role for ATR in the epigenetic regulation of gene expression and presents a new technique for ablating gene function in the germline.
|
|
| 19. |
- Sabouri, Nasim, et al.
(författare)
-
DNA replication through hard-to-replicate sites, including both highly transcribed RNA Pol II and Pol III genes, requires the S. pombe Pfh1 helicase
- 2012
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 26:6, s. 581-593
-
Tidskriftsartikel (refereegranskat)abstract
- Replication forks encounter impediments as they move through the genome, including natural barriers due to stable protein complexes and highly transcribed genes. Unlike lesions generated by exogenous damage, natural barriers are encountered in every S phase. Like humans, Schizosaccharomyces pombe encodes a single Pif1 family DNA helicase, Pfh1. Here, we show that Pfh1 is required for efficient fork movement in the ribosomal DNA, the mating type locus, tRNA, 5S ribosomal RNA genes, and genes that are highly transcribed by RNA polymerase II. In addition, converged replication forks accumulated at all of these sites in the absence of Pfh1. The effects of Pfh1 on DNA replication are likely direct, as it had high binding to sites whose replication was impaired in its absence. Replication in the absence of Pfh1 resulted in DNA damage specifically at those sites that bound high levels of Pfh1 in wild-type cells and whose replication was slowed in its absence. Cells depleted of Pfh1 were inviable if they also lacked the human TIMELESS homolog Swi1, a replisome component that stabilizes stalled forks. Thus, Pfh1 promotes DNA replication and separation of converged replication forks and suppresses DNA damage at hard-to-replicate sites.
|
|
| 20. |
- Swartling, Fredrik Johansson, et al.
(författare)
-
Pleiotropic role for MYCN in medulloblastoma
- 2010
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 24:10, s. 1059-1072
-
Tidskriftsartikel (refereegranskat)abstract
- Medulloblastoma (MB) is the most common malignant brain tumor of childhood. Sonic Hedgehog (SHH) signaling drives a minority of MB, correlating with desmoplastic pathology and favorable outcome. The majority, however, arises independently of SHH and displays classic or large cell anaplastic (LCA) pathology and poor prognosis. To identify common signaling abnormalities, we profiled mRNA, demonstrating misexpression of MYCN in the majority of human MB and negligible expression in normal cerebella. We clarified a role in pathogenesis by targeting MYCN (and luciferase) to cerebella of transgenic mice. MYCN-driven MB showed either classic or LCA pathologies, with Shh signaling activated in approximately 5% of tumors, demonstrating that MYCN can drive MB independently of Shh. MB arose at high penetrance, consistent with a role for MYCN in initiation. Tumor burden correlated with bioluminescence, with rare metastatic spread to the leptomeninges, suggesting roles for MYCN in both progression and metastasis. Transient pharmacological down-regulation of MYCN led to both clearance and senescence of tumor cells, and improved survival. Targeted expression of MYCN thus contributes to initiation, progression, and maintenance of MB, suggesting a central role for MYCN in pathogenesis.
|
|
| 21. |
- Venteclef, N, et al.
(författare)
-
GPS2-dependent corepressor/SUMO pathways govern anti-inflammatory actions of LRH-1 and LXRbeta in the hepatic acute phase response
- 2010
-
Ingår i: Genes & development. - : Cold Spring Harbor Laboratory. - 1549-5477 .- 0890-9369. ; 24:4, s. 381-395
-
Tidskriftsartikel (refereegranskat)abstract
- The orphan receptor LRH-1 and the oxysterol receptors LXRα and LXRβ are established transcriptional regulators of lipid metabolism that appear to control inflammatory processes. Here, we investigate the anti-inflammatory actions of these nuclear receptors in the hepatic acute phase response (APR). We report that selective synthetic agonists induce SUMOylation-dependent recruitment of either LRH-1 or LXR to hepatic APR promoters and prevent the clearance of the N-CoR corepressor complex upon cytokine stimulation. Investigations of the APR in vivo, using LXR knockout mice, indicate that the anti-inflammatory actions of LXR agonists are triggered selectively by the LXRβ subtype. We further find that hepatic APR responses in small ubiquitin-like modifier-1 (SUMO-1) knockout mice are increased, which is due in part to diminished LRH-1 action at APR promoters. Finally, we provide evidence that the metabolically important coregulator GPS2 functions as a hitherto unrecognized transrepression mediator of interactions between SUMOylated nuclear receptors and the N-CoR corepressor complex. Our study extends the knowledge of anti-inflammatory mechanisms and pathways directed by metabolic nuclear receptor–corepressor networks to the control of the hepatic APR, and implies alternative pharmacological strategies for the treatment of human metabolic diseases associated with inflammation.
|
|
| 22. |
- Wilhelm, MT, et al.
(författare)
-
Isoform-specific p73 knockout mice reveal a novel role for delta Np73 in the DNA damage response pathway
- 2010
-
Ingår i: Genes & development. - : Cold Spring Harbor Laboratory. - 1549-5477 .- 0890-9369. ; 24:6, s. 549-560
-
Tidskriftsartikel (refereegranskat)abstract
- Mice with a complete deficiency of p73 have severe neurological and immunological defects due to the absence of all TAp73 and ΔNp73 isoforms. As part of our ongoing program to distinguish the biological functions of these isoforms, we generated mice that are selectively deficient for the ΔNp73 isoform. Mice lacking ΔNp73 (ΔNp73−/− mice) are viable and fertile but display signs of neurodegeneration. Cells from ΔNp73−/− mice are sensitized to DNA-damaging agents and show an increase in p53-dependent apoptosis. When analyzing the DNA damage response (DDR) in ΔNp73−/− cells, we discovered a completely new role for ΔNp73 in inhibiting the molecular signal emanating from a DNA break to the DDR pathway. We found that ΔNp73 localizes directly to the site of DNA damage, can interact with the DNA damage sensor protein 53BP1, and inhibits ATM activation and subsequent p53 phosphorylation. This novel finding may explain why human tumors with high levels of ΔNp73 expression show enhanced resistance to chemotherapy.
|
|
| 23. |
- Yadav, Ram Kishor, et al.
(författare)
-
WUSCHEL protein movement mediates stem cell homeostasis in the Arabidopsis shoot apex
- 2011
-
Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 1549-5477 .- 0890-9369. ; 25:19, s. 2025-2030
-
Tidskriftsartikel (refereegranskat)abstract
- WUSCHEL (WUS) is a homeodomain transcription factor produced in cells of the niche/organizing center (OC) of shoot apical meristems. WUS specifies stem cell fate and also restricts its own levels by activating a negative regulator, CLAVATA3 (CLV3), in adjacent cells of the central zone (CZ). Here we show that the WUS protein, after being synthesized in cells of the OC, migrates into the CZ, where it activates CLV3 transcription by binding to its promoter elements. Using a computational model, we show that maintenance of the WUS gradient is essential to regulate stem cell number. Migration of a stem cell-inducing transcription factor into adjacent cells to activate a negative regulator, thereby restricting its own accumulation, is a theme that is unique to plant stem cell niches.
|
|
