Fig 1.

Ess1 preferentially associates with pSer5 CTD in vivo and promotes dephosphorylation of pSer7 CTD. (A) Wild-type (WT) cells were subjected to immunoprecipitation (IP) with anti-Ess1 polyclonal antibodies, followed by Western analysis with monoclonal antibodies H5 (P-Ser2), H14 (P-Ser5), and 8WG16 (hypophosphorylated CTD). Sample inputs (In) are indicated. Note that the H14 antibody actually recognizes doubly phosphorylated pSer2/pSer5 (11). (B) Western analysis of protein (10 μg) from whole-cell extracts of the indicated strains grown at 30°C. The 4E12 monoclonal antibody was used to detect levels of pSer7 CTD, and the 8WG16 monoclonal antibody (hypophosphorylated CTD) as a control for overall levels of RNA pol II CTD. Antitubulin antibodies were used for detection of the loading control. Note that ESS1 is an essential gene but can be suppressed by deletion of SRB10 (62).