Differential nuclear localization of the major adenovirus type 2 E1a proteins

The localization in infected and transformed cells of the two major adenovirus type 2 E1a proteins, of 289 and 243 amino acid residues, was studied with antisera raised against synthetic peptides or a TrpE-E1a fusion protein. Both E1a proteins were detected only in the nucleus of infected cells as determined by immunofluorescence analysis of cells infected with wild-type virus or with the mutants pm975 or dl1500, which produce, respectively, only the 289-residue or only the 243-residue E1a protein. However, the 289-residue protein was more tightly associated with the nucleus than was the 243-residue protein, as determined by the stability of nuclear fluorescence to different fixation procedures and by the use of radioimmunoprecipitation and Western blot analysis to analyze fractions extracted from the nucleus by detergent and other treatments. The latter experiments revealed that only the 289-residue protein, and only a fraction of that protein present in the nucleus, is associated with the nuclear matrix, both in infected HeLa cells and in the transformed human cell line 293.