Figure 4.

SRm160/300 interacts with the ESE-binding protein hTra2β. Immunoprecipitates were collected from HeLa nuclear extract by using mAb-B1C8 (lanes 4 and 5) and a control mAb (B3; specific for the hyperphosphorylated large subunit of RNA polymerase II; lane 3), transferred to nitrocellulose, and immunoblotted with an affinity-purified anti-peptide antibody specific for hTra2β. Total nuclear extract separated in lanes 1 and 2 represents approximately 10% of the amount of extract used in each immunoprecipitation. Nuclear extract was preincubated in the presence (lanes 1, 3, and 4) or absence (lanes 2 and 5) of ribonuclease before immunoprecipitation. Size markers (in kDa) and the rabbit IgG (Ig) heavy chain, derived from rabbit anti-mouse antibody used to couple mAbs B1C8 and B3 to protein A-Sepharose, are indicated.