High impact information on RPB9

• RPB9 appears to play a unique role in transcription initiation, as the defects revealed in its absence are distinct from those seen with mutants in RNA polymerase subunit RPB1 and factor e (TFIIB), two other yeast proteins also involved in start site selection [1].
• Simultaneous deletion of RPB9 and RAD26 genes completely abolishes TCR in both the coding and upstream regions, indicating that no other TCR subpathway exists in RNA polymerase II-transcribed genes [2].
• Rpb4 and Rpb9 mediate subpathways of transcription-coupled DNA repair in Saccharomyces cerevisiae [2].
• Genes encoding homologs of the related eucaryal RNAP subunits A12.2/B12.6 and also homologs of eucaryal transcription elongation factors of the TFIIS family have been detected in Sulfolobus acidocaldarius and Thermococcus celer [3].
• Evidence that the Transcription Elongation Function of Rpb9 Is Involved in Transcription-Coupled DNA Repair in Saccharomyces cerevisiae [4].

Biological context of RPB9

• These results establish a functional interaction between TFIIB and the Rpb9 subunit of RNA polymerase II and suggest that these two components of the preinitiation complex interact during transcription start site selection [5].
• Recessive mutations in the SSU71, SSU72 and SSU73 genes of Saccharomyces cerevisiae were identified as either suppressors or enhancers of a TFIIB defect (sua7-1) that confers both a cold-sensitive growth phenotype and a downstream shift in transcription start site selection [5].
• Here, we show that RPB9 has a synthetic phenotype with the TFIIS gene [6].
• The amino acid sequence of the RRN4 protein (A12.2) is similar to that of the RPB9 (B12.6) subunit of yeast RNA polymerase II; the similarity includes the presence of two putative zinc-binding domains [7].
• RPB9 is a single copy gene on chromosome VII [8].

Associations of RPB9 with chemical compounds

• Disruption of RPB9 in yeast also resulted in sensitivity to 6-azauracil, which is a phenotype linked to defects in transcription elongation [6].

Physical interactions of RPB9

• In a two-hybrid test, Rpb9 physically interacts with Tfa1, the largest subunit of TFIIE [9].

Regulatory relationships of RPB9

• The RPB9 subunit of RNA polymerase II regulates transcription elongation activity and is required for the action of the transcription elongation factor, TFIIS [10].
• The Zn2 domain, which is dispensable for transcription elongation and TCR functions, is essential for Rpb9 to promote Rpb1 degradation, whereas the Zn1 and linker domains, which are essential for transcription elongation and TCR functions, play a subsidiary role in Rpb1 degradation [11].

Other interactions of RPB9

• The Rpb2-Rpb9 "lobe-jaw" region of RNAP II is downstream of the catalytic center and distal to the site of RNAP II-TFIIB interaction [12].
• RNA polymerase II lacking the Rpb9 subunit uses alternate transcription initiation sites in vitro and in vivo and is unable to respond to the transcription elongation factor TFIIS in vitro [6].

Analytical, diagnostic and therapeutic context of RPB9

• Immunoprecipitation of RNA polymerase II from cells lacking the RPB9 gene revealed that all of the remaining 11 subunits are assembled into the enzyme, suggesting that the start site defect is attributable solely to the absence of RPB9 [1].

References