| 1. |
- Kim, Y J, et al.
(författare)
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A multiprotein mediator of transcriptional activation and its interaction with the C-terminal repeat domain of RNA polymerase II.
- 1994
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Ingår i: Cell. - 0092-8674 .- 1097-4172. ; 77:4, s. 599-608
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Tidskriftsartikel (refereegranskat)abstract
- A mediator was isolated from yeast that enabled a response to the activator proteins GAL4-VP16 and GCN4 in a transcription system reconstituted with essentially homogeneous basal factors and RNA polymerase II. The mediator comprised some 20 polypeptides, including the three subunits of TFIIF and other polypeptides cross-reactive with antisera against GAL11, SUG1, SRB2, SRB4, SRB5, and SRB6 proteins. Mediator not only enabled activated transcription but also conferred 8-fold greater activity in basal transcription and 12-fold greater efficiency of phosphorylation of RNA polymerase II by the TFIIH-associated C-terminal repeat domain (CTD) kinase, indicative of mediator-CTD interaction. A holoenzyme form of RNA polymerase II was independently isolated that supported a response to activator proteins with purified basal factors. The holoenzyme proved to consist of mediator associated with core 12-subunit RNA polymerase II.
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| 2. |
- Pfarr, C. M., et al.
(författare)
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Mouse JunD negatively regulates fibroblast growth and antagonizes transformation by ras
- 1994
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Ingår i: Cell. - : Cell Press. - 0092-8674 .- 1097-4172. ; 76:4, s. 747-760
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Tidskriftsartikel (refereegranskat)abstract
- As NIH 3T3 fibroblasts become quiescent, the level of c-Jun protein decreases while JunD accumulates. When resting cells are stimulated with fresh serum, nuclear-localized JunD is rapidly degraded, followed by resynthesis of both c-Jun and JunD later in G1. Overexpression of JunD results in slower growth and an increase in the percentage of cells in G0/G1 while c-Jun overexpression produces larger S/G2 and M phase populations. In addition, JunD partially suppresses transformation by an activated ras gene whereas c-Jun cooperates with ras to transform cells. These data indicate that two closely related transcription factors can function in an opposing manner.
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| 3. |
- Åström, Stefan U, et al.
(författare)
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Rit1, a tRNA backbone-modifying enzyme that mediates initiator and elongator tRNA discrimination
- 1994
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Ingår i: Cell. - : Elsevier. - 0092-8674 .- 1097-4172. ; 79:3, s. 535-546
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Tidskriftsartikel (refereegranskat)abstract
- Using a genetic screen in yeast aimed at identifying cellular factors involved in initiator and elongator methionine tRNA discrimination in the translational process, we have identified a mutation that abolish the requirement for elongator methionine tRNA. The gene affected, which we call the ribosylation of the initiator tRNA gene or RIT1, encodes a 2'-O-ribosyl phosphate transferase. This enzyme modifies exclusively the initiator tRNA in position 64 using 5'-phosphoribosyl-1'-pyrophosphate as the modification donor. As the initiator tRNA participates both in the initiation and elongation of translation in a rit1 strain, we conclude that the 2'-O-ribosyl phosphate modification discriminates the initiator tRNAs from the elongator tRNAs during protein synthesis. The modification enzyme was shown to recognize the stem-loop IV region that is unique in eukaryotic cytoplasmic initiator tRNAs.
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