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| 2. |
- Djupedal, Ingela, et al.
(författare)
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RNA Pol II subunit Rpb7 promotes centromeric transcription and RNAi-directed chromatin silencing
- 2005
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Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 19:19, s. 2301-2306
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Tidskriftsartikel (refereegranskat)abstract
- Fission yeast centromeric repeats are transcribed into small interfering RNA (siRNA) precursors (pre-siRNAs), which are processed by Dicer to direct heterochromatin formation. Recently, Rpb1 and Rpb2 subunits of RNA polymerase II (RNA Pol II) were shown to mediate RNA interference (RNAi)-directed chromatin modification but did not affect pre-siRNA levels. Here we show that another Pol II subunit, Rpb7 has a specific role in presiRNA transcription. We define a centromeric presiRNA promoter from which initiation is exquisitely sensitive to the rpb7-G150D mutation. In contrast to other Pol II subunits, Rpb7 promotes pre-siRNA transcription required for RNAi-directed chromatin silencing.
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| 3. |
- Spåhr, H, et al.
(författare)
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Analysis of Schizosaccharomyces pombe mediator reveals a set of essential subunits conserved between yeast and metazoan cells.
- 2001
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 98:21, s. 11985-90
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Tidskriftsartikel (refereegranskat)abstract
- With the identification of eight new polypeptides, we here complete the subunit characterization of the Schizosaccharomyces pombe RNA polymerase II holoenzyme. The complex contains homologs to all 10 essential gene products present in the Saccharomyces cerevisiae Mediator, but lacks clear homologs to any of the 10 S. cerevisiae components encoded by nonessential genes. S. pombe Mediator instead contains three unique components (Pmc2, -3, and -6), which lack homologs in other cell types. Presently, pmc2(+) and pmc3(+) have been shown to be nonessential genes. The data suggest that S. pombe and S. cerevisiae share an essential protein module, which associates with nonessential speciesspecific subunits. In support of this view, sequence analysis of the conserved yeast Mediator components Med4 and Med8 reveals sequence homology to the metazoan Mediator components Trap36 and Arc32. Therefore, 8 of 10 essential genes conserved between S. pombe and S. cerevisiae also have a metazoan homolog, indicating that an evolutionary conserved Mediator core is present in all eukaryotic cells. Our data suggest a closer functional relationship between yeast and metazoan Mediator than previously anticipated.
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| 4. |
- Spåhr, H, et al.
(författare)
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Purification and characterization of RNA polymerase II holoenzyme from Schizosaccharomyces pombe.
- 2000
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Ingår i: The Journal of biological chemistry. - : Elsevier BV. - 0021-9258. ; 275:2, s. 1351-6
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Tidskriftsartikel (refereegranskat)abstract
- We have purified the RNA polymerase II holoenzyme from Schizosaccharomyces pombe to near homogeneity. The Mediator complex is considerably smaller than its counterpart in Saccharomyces cerevisiae, containing only nine polypeptides larger than 19 kDa. Five of these Mediator subunits have been identified as the S. pombe homologs to Rgr1, Srb4, Med7, and Nut2 found in S. cerevisiae and the gene product of a previously uncharacterized open reading frame, PMC2, with no clear homologies to any described protein. The presence of Mediator in a S. pombe RNA polymerase II holoenzyme stimulated phosphorylation of the C-terminal domain by TFIIH purified from S. pombe. This stimulation was species-specific, because S. pombe Mediator could not stimulate TFIIH purified from S. cerevisiae. We suggest that the overall structure and mechanism of the Mediator is evolutionary conserved. The subunit composition, however, has evolved to respond properly to physiological signals.
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