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- Bergquist, Helen, 1979-
(författare)
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Development of benzoquinoquinoxaline derivatives as triplex-specific probes : Recognition of DNA structures at repeats sequences
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Repeat sequences are associated with several human diseases, such as Friedreich’s ataxia, polycystic kidney disease and cancer. These sequences can form non-B-DNA structures, including triplex (H-DNA) DNA, and are associated with genomic instability and altered gene expression. The occurrence of triplex structures in vivo and identification of their links to biological processes have been challenging. The lack of effective probes has restrained the study of triplex structures in living cells. Here, the triplex binding small molecule benzoquinoquinoxaline (BQQ) and its derivatives were developed as tools to study triplex formation at genomic repeat sequences. The triplex binding efficiency towards both purine and pyrimidine triplex motifs was determined for BQQ, the DNA cleaving BQQ-1,10-(ortho)-phenanthroline (BQQ-OP) and the fluorescent BQQ-Bodipy compounds. BQQ was shown to have the most stabilising effect on both triplex motifs. Moreover, H-DNA structure formation at a pkd1 derived sequence was demonstrated for the first time by BQQ-OP at physiologically relevant conditions. H-DNA formation was also shown at (GAA)n repeats associated with Friedreich’s ataxia and the structure was further analysed on one nucleotide resolution, confirming that (GAA)n repeats form a pyrimidine H-DNA. However, a mixture of different isomers formed at longer (GAA)n repeats. To this end, the interaction between the peptide nucleic acids (PNA) and BQQ was investigated. PNA is a DNA mimic that binds sequence-specifically to dsDNA and can form several PNA-DNA complexes. The results of PNA binding to frataxin (GAA)n expansion in plasmid were evaluated, and in the presence of GAA-PNA no triplex structure could be detected by BQQ-OP cleavage. When the structure formed in the presence of either GAA-PNA or CTT-PNA was further analysed, it was found that GAA-PNA formed a duplex invasion complex preventing H-DNA formation, whereas CTT-PNA formed a triplex invasion complex.
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| 3. |
- Bergquist, Helen, et al.
(författare)
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Disruption of Higher Order DNA Structures in Friedreich's Ataxia (GAA)(n) Repeats by PNA or LNA Targeting
- 2016
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Ingår i: PLOS ONE. - : PLOS. - 1932-6203. ; 11:11
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Tidskriftsartikel (refereegranskat)abstract
- Expansion of (GAA)(n) repeats in the first intron of the Frataxin gene is associated with reduced mRNA and protein levels and the development of Friedreich's ataxia. (GAA)(n) expansions form non-canonical structures, including intramolecular triplex (H-DNA), and Rloops and are associated with epigenetic modifications. With the aim of interfering with higher order H-DNA (like) DNA structures within pathological (GAA)(n) expansions, we examined sequence-specific interaction of peptide nucleic acid (PNA) with (GAA)(n) repeats of different lengths (short: n= 9, medium: n= 75 or long: n= 115) by chemical probing of triple helical and single stranded regions. We found that a triplex structure (H-DNA) forms at GAA repeats of different lengths; however, single stranded regions were not detected within the medium size pathological repeat, suggesting the presence of a more complex structure. Furthermore, (GAA) 4-PNA binding of the repeat abolished all detectable triplex DNA structures, whereas (CTT) 5-PNA did not. We present evidence that (GAA) 4-PNA can invade the DNA at the repeat region by binding the DNA CTT strand, thereby preventing non-canonical-DNA formation, and that triplex invasion complexes by (CTT) 5-PNA form at the GAA repeats. Locked nucleic acid (LNA) oligonucleotides also inhibited triplex formation at GAA repeat expansions, and atomic force microscopy analysis showed significant relaxation of plasmid morphology in the presence of GAA-LNA. Thus, by inhibiting disease related higher order DNA structures in the Frataxin gene, such PNA and LNA oligomers may have potential for discovery of drugs aiming at recovering Frataxin expression.
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| 7. |
- Bergquist, Helen, et al.
(författare)
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Structural Insights into Human Adenovirus Type 4 Virus-Associated RNA I
- 2022
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 23:6
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Tidskriftsartikel (refereegranskat)abstract
- RNA molecules can adopt specific RNA triplex structures to execute critical biological functions. Human adenoviruses (HAdVs) are abundant pathogens encoding the essential, noncoding virus-associated RNA I (VA RNAI). Here, we employ a triplex-specific probing assay, based on the intercalating and cleaving agent benzoquinoquinoxaline 1, 10-phenanthroline (BQQ-OP), to unravel a potential RNA triplex formation in VA RNAI. The BQQ-OP cleavage of the pathogenic HAdV type 4 (HAdV-4) VA RNAI indicates that a potential triplex is formed involving the highly conserved stem 4 of the central domain and side stem 7. Further, the integrity of the HAdV-4 VA RNAI side stem 7 contributes to a potential triplex formation in vitro and virus growth in vivo. Collectively, we propose that the HAdV-4 VA RNAI can potentially form a biologically relevant triplex structure.
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| 9. |
- Bergquist, Helen, 1979-, et al.
(författare)
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Structure-Specific Recognition of Friedreich’s Ataxia (GAA)n Repeats by Benzoquinoquinoxaline Derivatives
- 2009
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Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 10:16, s. 2629-2637
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Tidskriftsartikel (refereegranskat)abstract
- Expansion of GAA triplet repeats in intron 1 of the FXN gene reduces frataxin expression and causes Friedreich's ataxia. (GAA)nrepeats form non-B-DNA structures, including triple helix H-DNA and higher-order structures (sticky DNA). In the proposed mechanisms of frataxin gene silencing, central unanswered questions involve the characterization of non-B-DNA structure(s) that are strongly suggested to play a role in frataxin expression. Here we examined (GAA)nbinding by triplex-stabilizing benzoquinoquinoxaline (BQQ) and the corresponding triplex-DNA-cleaving BQQ-1,10-phenanthroline (BQQ-OP) compounds. We also examined the ability of these compounds to act as structural probes for H-DNA formation within higher-order structures at pathological frataxin sequences in plasmids. DNA-complex-formation analyses with a gel-mobility-shift assay and sequence-specific probing of H-DNA-forming (GAA)nsequences by single-strand oligonucleotides and triplex-directed cleavage demonstrated that a parallel pyrimidine (rather than purine) triplex is the more stable motif formed at (GAA)nrepeats under physiologically relevant conditions.
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| 10. |
- Deng, Tingzhi, et al.
(författare)
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Hippocampal Transcriptome-Wide Association Study Reveals Correlations Between Impaired Glutamatergic Synapse Pathway and Age-Related Hearing Loss in BXD-Recombinant Inbred Mice
- 2021
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Ingår i: Frontiers in Neuroscience. - : Frontiers Media S.A.. - 1662-4548 .- 1662-453X. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Age-related hearing loss (ARHL) is associated with cognitive dysfunction; however, the detailed underlying mechanisms remain unclear. The aim of this study is to investigate the potential underlying mechanism with a system genetics approach. A transcriptome-wide association study was performed on aged (12-32 months old) BXD mice strains. The hippocampus gene expression was obtained from 56 BXD strains, and the hearing acuity was assessed from 54 BXD strains. Further correlation analysis identified a total of 1,435 hearing-related genes in the hippocampus (p < 0.05). Pathway analysis of these genes indicated that the impaired glutamatergic synapse pathway is involved in ARHL (p = 0.0038). Further gene co-expression analysis showed that the expression level of glutamine synthetase (Gls), which is significantly correlated with ARHL (n = 26, r = -0.46, p = 0.0193), is a crucial regulator in glutamatergic synapse pathway and associated with learning and memory behavior. In this study, we present the first systematic evaluation of hippocampus gene expression pattern associated with ARHL, learning, and memory behavior. Our results provide novel potential molecular mechanisms involved in ARHL and cognitive dysfunction association.
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