| 1. |
- Björk, Glenn R, et al.
(författare)
-
A primordial tRNA modification required for the evolution of life?
- 2001
-
Ingår i: EMBO Journal. - : Wiley. - 0261-4189 .- 1460-2075. ; 20:1-2, s. 231-239
-
Tidskriftsartikel (refereegranskat)abstract
- The evolution of reading frame maintenance must have been an early event, and presumably preceded the emergence of the three domains Archaea, Bacteria and Eukarya. Features evolved early in reading frame maintenance may still exist in present-day organisms. We show that one such feature may be the modified nucleoside 1-methylguanosine (m(1)G37), which prevents frameshifting and is present adjacent to and 3' of the anticodon (position 37) in the same subset of tRNAs from all organisms, including that with the smallest sequenced genome (Mycoplasma genitalium), and organelles. We have identified the genes encoding the enzyme tRNA(m(1)G37)methyltransferase from all three domains. We also show that they are orthologues, and suggest that they originated from a primordial gene. Lack of m(1)G37 severely impairs the growth of a bacterium and a eukaryote to a similar degree. Yeast tRNA(m(1)G37)methyltransferase also synthesizes 1-methylinosine and participates in the formation of the Y-base (yW). Our results suggest that m(1)G37 existed in tRNA before the divergence of the three domains, and that a tRNA(m(1)G37)methyltrans ferase is part of the minimal set of gene products required for life.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Johansson, Marcus J O, et al.
(författare)
-
Dual function of the tRNA(m(5)U54)methyltransferase in tRNA maturation
- 2002
-
Ingår i: RNA. - 1355-8382 .- 1469-9001. ; 8:3, s. 324-335
-
Tidskriftsartikel (refereegranskat)abstract
- A 5-methyluridine (m(5)U) residue at position 54 is a conserved feature of bacterial and eukaryotic tRNAs. The methylation of U54 is catalyzed by the tRNA(m5U54)methyltransferase, which in Saccharomyces cerevisiae is encoded by the nonessential TRM2 gene. In this study, we identified four different strains with mutant forms of tRNA(Ser)CGA. The absence of the TRM2 gene in these strains decreased the stability of tRNA(Ser)CGA and induced lethality. Two alleles of TRM2 encoding catalytically inactive tRNA(m5U54)methyltransferases were able to stabilize tRNA(Ser)CGA in one of the mutants, revealing a role for the Trm2 protein per se in tRNA maturation. Other tRNA modification enzymes interacting with tRNA(Ser)CGA in the maturation process, such as Pus4p, Trm1 p, and Trm3p were essential or important for growth of the tRNA(Ser)CGA mutants. Moreover, Lhp1p, a protein binding RNA polymerase III transcripts, was required to stabilize the mutant tRNAs. Based on our results, we suggest that tRNA modification enzymes might have a role in tRNA maturation not necessarily linked to their known catalytic activity.
|
|
| 5. |
- Johansson, Marcus J O, et al.
(författare)
-
The Saccharomyces cerevisiae TAN1 gene is required for N4-acetylcytidine formation in tRNA.
- 2004
-
Ingår i: RNA. - 1355-8382. ; 10:4, s. 712-9
-
Tidskriftsartikel (refereegranskat)abstract
- The biogenesis of transfer RNA is a process that requires many different factors. In this study, we describe a genetic screen aimed to identify gene products participating in this process. By screening for mutations lethal in combination with a sup61-T47:2C allele, coding for a mutant form of, the nonessential TAN1 gene was identified. We show that the TAN1 gene product is required for formation of the modified nucleoside N(4)-acetylcytidine (ac(4)C) in tRNA. In Saccharomyces cerevisiae, ac(4)C is present at position 12 in tRNAs specific for leucine and serine as well as in 18S ribosomal RNA. Analysis of RNA isolated from a tan1-null mutant revealed that ac(4)C was absent in tRNA, but not rRNA. Although no tRNA acetyltransferase activity by a GST-Tan1 fusion protein was detected, a gel-shift assay revealed that Tan1p binds tRNA, suggesting a direct role in synthesis of ac(4)C(12). The absence of the TAN1 gene in the sup61-T47:2C mutant caused a decreased level of mature, indicating that ac(4)C(12) and/or Tan1p is important for tRNA stability.
|
|
| 6. |
- Johansson, Sveneric, et al.
(författare)
-
New forbidden and fluorescence Fe III lines identified in HST spectra of eta Carinae
- 2001
-
Ingår i: Astronomy and Astrophysics. - 1432-0746. ; 361, s. 977-977
-
Tidskriftsartikel (refereegranskat)abstract
- We discuss the origin of eight emission lines in the spectra of gas blobs close to the central star of eta Carinae. The spectra have been obtained with the Goddard High Resolution Spectrograph (GHRS) and the Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope. Between 2400 and 2500 Å five narrow lines are identified as new forbidden lines of doubly ionized iron, [Fe III]. We present gA-value data for the corresponding transitions, which combine two different metastable configurations of Fe III. An anomalous intensity of the narrow Fe III line (UV 34) at 1914 Å is explained as fluorescence due to HLyalpha pumping. A level mixing of about 1% increases the f-value of the pumped excitation channel by more than two orders of magnitude, which makes the pumping efficient and the fluorescence significant. We introduce a new designation for fluorescence lines photoexcited by an accidental resonance, eg. < Fe III> in the case of doubly ionized iron. Based on observations with the NASA/ESA Hubble Space Telescope, and supported by grant numbers GO-6501 and GO-7302 from the Space Telescope Science Institute. The STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.
|
|
| 7. |
- Nordlund, Monica E, et al.
(författare)
-
Identification of the TRM2 gene encoding the tRNA(m5U54)methyltransferase of Saccharomyces cerevisiae.
- 2000
-
Ingår i: RNA. - 1355-8382 .- 1469-9001. ; 6:6, s. 844-60
-
Tidskriftsartikel (refereegranskat)abstract
- The presence of 5-methyluridine (m5U) at position 54 is a ubiquitous feature of most bacterial and eukaryotic elongator tRNAs. In this study, we have identified and characterized the TRM2 gene that encodes the tRNA(m5U54)methyltransferase, responsible for the formation of this modified nucleoside in Saccharomyces cerevisiae. Transfer RNA isolated from TRM2-disrupted yeast strains does not contain the m5U54 nucleoside. Moreover, a glutathione S-transferase (GST) tagged recombinant, Trm2p, expressed in Escherichia coli displayed tRNA(m5U54)methyltransferase activity using as substrate tRNA isolated from a trm2 mutant strain, but not tRNA isolated from a TRM2 wild-type strain. In contrast to what is found for the tRNA(m5U54)methyltransferase encoding gene trmA+ in E. coli, the TRM2 gene is not essential for cell viability and a deletion strain shows no obvious phenotype. Surprisingly, we found that the TRM2 gene was previously identified as the RNC1/NUD1 gene, believed to encode the yNucR endo-exonuclease. The expression and activity of the yNucR endo-exonuclease is dependent on the RAD52 gene, and does not respond to increased gene dosage of the RNC1/NUD1 gene. In contrast, we find that the expression of a trm2-LacZ fusion and the activity of the tRNA(m5U54)methyltransferase is not regulated by the RAD52 gene and does respond on increased gene dosage of the TRM2 (RNC1/NUD1) gene. Furthermore, there was no nuclease activity associated with a GST-Trm2 recombinant protein. The purified yNucR endo-exonuclease has been reported to have an NH2-D-E-K-N-L motif, which is not found in the Trm2p. Therefore, we suggest that the yNucR endo-exonuclease is encoded by a gene other than TRM2.
|
|
| 8. |
|
|
