Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A transcription factor designated SIII was recently purified from mammalian cells and shown to regulate the activity of the RNA polymerase II elongation complex. SIII is a heterotrimer composed of approximately 110-, 18-, and 15-kDa polypeptides and is capable of increasing the overall rate of RNA chain elongation by RNA polymerase II by suppressing transient pausing of polymerase at multiple sites on the DNA template. Here we describe the molecular cloning and characterization of a cDNA encoding the functional 15-kDa subunit (p15) of SIII. The p15 cDNA encodes a 112-amino-acid polypeptide with a calculated molecular mass of 12,473 Da and an electrophoretic mobility indistinguishable from that of the natural p15 subunit. When combined with the 110- and 18-kDa SIII subunits, bacterially expressed p15 efficiently replaces the natural p15 subunit in reconstitution of transcriptionally active SIII. A homology search revealed that the amino-terminal half of the SIII p15 subunit shares significant sequence similarity with a portion of the RNA-binding domain of Escherichia coli transcription termination protein rho and with the E. coli NusB protein, suggesting that SIII may be evolutionarily related to proteins involved in the control of transcription elongation in eubacteria.
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PMID:Molecular cloning of an essential subunit of RNA polymerase II elongation factor SIII. 820 74

Inactivating mutations of the von Hippel-Lindau (VHL) tumor suppressor gene cause the VHL cancer syndrome and sporadic renal clear cell carcinoma. VHL engages in a nucleocytoplasmic shuttle, which is required for its function. Here, we pursue our investigation to identify mechanisms by which VHL-green fluorescent protein (VHL-GFP) is exported from the nucleus. We show that nuclear export of VHL-GFP in living cells requires ongoing RNA polymerase II activity, and is mediated by mechanisms that are temperature-sensitive and energy-dependent. In vitro nuclear export of VHL-GFP is inhibited by nuclear pore-specific lectins, requires ATP hydrolysis and polyadenylated mRNAs, and occurs with kinetics that are similar to those of proteins containing a nuclear export signal. Biochemical fractionation has revealed that nuclear export of VHL-GFP occurs by way of a Ran-dependent pathway. Size exclusion column chromatography and deletion mutant analysis suggest that VHL-GFP does not require assembly with one of its associated proteins, cullin-2, to engage in nuclear export. These results demonstrate that nuclear export of VHL-GFP is Ran-mediated and ATP hydrolysis-dependent. They also suggest that sequences outside the elongin C binding box may function as a nuclear export domain, potentially providing a novel role for this region of VHL frequently mutated in renal cell carcinoma.
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PMID:Ran-mediated nuclear export of the von Hippel-Lindau tumor suppressor protein occurs independently of its assembly with cullin-2. 1072 48

Elongin is a transcription elongation factor that was first identified in mammalian systems and is composed of the three subunits, elongin A, B, and C. Sequence homologues of elongin A and elongin C, but not elongin B, were identified in the yeast genome. Neither yeast elongin A nor C sequence homologues was required for cell viability. The two gene products could be purified from yeast as a complex. A recombinant form of the complex, which could only be produced in bacteria if the gene products were co-expressed, was purified over several chromatographic steps. The complex did not stimulate transcription elongation by yeast RNA polymerase II. Using limited proteolysis, the N-terminal 144 residues of yeast elongin A were shown to be sufficient for interaction with yeast elongin C. The purified complex of yeast elongin C/elongin A(1-143) was analyzed using circular dichroism and nuclear magnetic spectroscopy. These studies revealed that yeast elongin A is unfolded but undergoes a dramatic modification of its structure in the presence of elongin C, and that elongin C forms a stable dimer in the absence of elongin A.
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PMID:Elongin from Saccharomyces cerevisiae. 1075 24

Elongin is a transcription elongation factor that stimulates the rate of elongation by suppressing transient pausing by RNA polymerase II at many sites along the DNA. It is heterotrimeric in mammals, consisting of elongins A, B and C subunits, and bears overall similarity to a class of E3 ubiquitin ligases known as SCF (Skp1-Cdc53 (cullin)-F-box) complexes. A subcomplex of elongins B and C is a target for negative regulation by the von Hippel-Lindau (VHL) tumor-suppressor protein. Elongin C from Saccharomyces cerevisiae, Elc1, exhibits high sequence similarity to mammalian elongin C. Using NMR spectroscopy we have determined the three-dimensional structure of Elc1 in complex with a human VHL peptide, VHL(157-171), representing the major Elc1 binding site. The bound VHL peptide is entirely helical. Elc1 utilizes two C-terminal helices and an intervening loop to form a binding groove that fits VHL(157-171). Chemical shift perturbation and dynamics analyses reveal that a global conformational change accompanies Elc1/VHL(157-171) complex formation. Moreover, the disappearance of conformational exchange phenomena on the microsecond to millisecond time scale within Elc1 upon VHL peptide binding suggests a role for slow internal motions in ligand recognition.
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PMID:Solution structure and dynamics of yeast elongin C in complex with a von Hippel-Lindau peptide. 1154 95

Treatment of yeast and human cells with DNA-damaging agents elicits lysine 48-linked polyubiquitylation of Rpb1, the largest subunit of RNA polymerase II (Pol II), which targets Pol II for proteasomal degradation. However, the ubiquitin ligase (E3) responsible for Pol II polyubiquitylation has not been identified in humans or the yeast Saccharomyces cerevisiae. Here we show that elongin A (Ela1) and cullin 3 (Cul3) are required for Pol II polyubiquitylation and degradation in yeast cells, and on the basis of these and other observations, we propose that an E3 comprised of elongin C (Elc1), Ela1, Cul3, and the RING finger protein Roc1 (Rbx1) mediates this process in yeast cells. This study provides, in addition to the identification of the E3 required for Pol II polyubiquitylation and degradation in yeast cells, the first evidence for a specific function in yeast for a member of the elongin C/BC-box protein/cullin family of ligases. Also, these observations raise the distinct possibility that the elongin C-containing ubiquitin ligase, the von Hippel-Lindau tumor suppressor complex, promotes Pol II polyubiquitylation and degradation in human cells.
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PMID:ELA1 and CUL3 are required along with ELC1 for RNA polymerase II polyubiquitylation and degradation in DNA-damaged yeast cells. 1729 27

Transcription coupled repair (TCR) is a nucleotide excision repair (NER) pathway that is dedicated to repair in the transcribed strand of an active gene. The genome overall NER is called global genomic repair (GGR). Elc1, the yeast homolog of the mammalian elongation factor elongin C, has been shown to be a component of a ubiquitin ligase complex that contains Rad7 and Rad16, two factors that are specifically required for GGR. Elc1 has also been suggested to be present in another ubiquitin ligase complex that lacks Rad7 and Rad16 and is involved in UV-induced ubiquitylation and subsequent degradation of RNA polymerase II. Here we show that elc1 deletion increases UV sensitivity of TCR-deficient cells but does not affect the UV sensitivity of otherwise wild type and GGR-deficient cells. Cells deleted for elc1 show normal NER in the transcribed strand of an active gene but have no detectable NER in the non-transcribed strand. Elc1 does not affect UV-induced mutagenesis when TCR is operative, but plays an important role in preventing the mutagenesis if TCR is defective. Furthermore, the levels of Rad7 and Rad16 proteins are not significantly decreased in elc1 cells, and overexpression of Rad7 and Rad16 individually or simultaneously in elc1 cells does not restore repair in the non-transcribed strand of an active gene. Our results suggest that Elc1 has no function in TCR but plays an important role in GGR. Furthermore, the role of Elc1 in GGR may not be subsidiary to that of Rad7 and Rad16.
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PMID:Yeast Elc1 plays an important role in global genomic repair but not in transcription coupled repair. 1881 98