Involvement of S. cerevisiae Rpb4 in subset of pathways related to transcription elongation

• We studied the transcription elongation defect of RNAP II lacking Rpb4.
• In rpb4∆, RNAPII did not show significant elongation defect on ORF of long gene.
• RPB4 shares strong genetic interaction with PAF1, SPT4, RPB9, DST1, ELP3 and GCN5.
• Rpb4 assists Paf1 in elongation of FKS1 gene under cellular stress condition.
• Rpb4 is required for elongation, in gene specific manner under certain conditions.

Yeast Rpb4, a subunit of RNA pol II is not essential for viability but is involved in multiple cellular phenotypes such as temperature sensitivity, enhanced pseudohyphal morphology, and decreased sporulation. Both in vivo and in vitro studies strongly support involvement of Rpb4 in transcription initiation, while its role in transcription elongation is not entirely consistent. Here we show that Rpb4 is not required for recruitment of RNA pol II on the coding region of YLR454w, a representative long gene. Yet we find strong genetic interaction of rpb4∆ with mutants in many transcription elongation factors such as Paf1, Spt4, Dst1, Elp3 and Rpb9. We demonstrate that, Rpb4 interacts functionally with Paf1 to affect the transcription elongation of the FKS1 gene. Our results suggest that while Rpb4 is not required for general transcription elongation, it could support transcription elongation for specific of class of genes by interaction with other elongation factors.