FIG. 1.

E1A stimulates the DNA binding activity of the E4F-N1 protein. (A) Gel shift analysis of E4F-N1 (E4F residues 84 to 262) DNA binding activity in extracts of HeLa cells transiently transfected with pCMVs-E4FN1 with or without pCMV-E1A(13S). Nuclear extracts (N.E.) were prepared 48 h posttransfection and step fractionated on heparin-agarose. (B) Western blots of whole-cell extracts (W.C.E.) from the transfected cells. E4F-N4-specific antiserum was used to detect E4F-N1 protein (top); monoclonal antibody M73 was used to detect E1A protein (bottom).