Sumoylation of RNA Polymerase II Regulates Transcription in Saccharomyces cerevisiae

Sumoylation is a post-translational modification that is involved in a host of cellular processes, including important roles in transcription. While it was previously reported that Rpb1, the largest subunit of RNA polymerase II (RNAPII), is sumoylated following UV-stress, our lab has shown that Rpb1 is also sumoylated under normal growth conditions. Here, we show that sumoylated Rpb1 is mostly associated with chromatin, providing further support for its role in transcriptional processes. We also show that the SUMO protease Ulp2 is important for supporting basal sumoylation of Rpb1, rather than merely as an instrument for desumoylation, which is an unexpected finding. Moreover, while impairing Rpb1 sumoylation at its major sumoylation site, K1487, has no apparent effect on growth, nascent transcription analysis from Global Run-on Sequencing (GROseq) reveals that a small number of genes are upregulated in this sumoylation-deficient Rpb1 mutant, a quarter of which are involved in the stress response.