Differential nuclear localization of the major adenovirus type 2 E1a proteins

Abstract

The localization in infected and transformed cells of the two major adenovirus type 2 Ela proteins, of 289 and 243 amino acid residues, was studied with antisera raised against synthetic peptides or a TrpE-Ela fusion protein. Both Ela 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 d11500, which produce, respectively, only the 289-residue or only the 243-residue Ela 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.

Differential distribution of the adenovirus E1A proteins and colocalization of E1A with the 70-kilodalton cellular heat shock protein in infected cells

“…la and b). This pattern of staining has previously been observed using antibodies specific for DNA and histones and resembles the previously reported staining pattern of the ElA proteins in infected cells (7,14,37). The second most abundant pattern was a reticular distribution ( Fig.…”

“…Utilizing polyclonal antibodies specific for the ElA 13S gene product, Feldman and Nevins (7) reported that the 289amino-acid protein is predominantly found in the nucleus of infected cells, with a portion being tightly associated with the insoluble nuclear matrix. With the availability of antibodies capable of recognizing both the 13S and 12S ElA gene products, as well as adenovirus mutants which express individual cDNA genes for the 13S and 12S mRNAs, it was found that both forms of ElA are predominantly localized within the nucleus of infected cells (14,37). It is the 13S and not the 12S product, however, that appears to be nuclear matrix associated in infected and transformed cells (37).…”

The terminal regions of adenovirus and minute virus of mice DNAs are preferentially associated with the nuclear matrix in infected cells

“…If viral DNA replication mimics DNA replication of the host cell with regard to nuclear compartmentalization, one would predict that regions of the viral genome that function as replication origins would be selectively enriched in the nuclear matrix fraction. Although previous studies had demonstrated that adenovirus and herpes simplex virus DNAs are matrix associated throughout the cycle of lytic infection in HeLa cells (7,60,67), as are several important early viral polypeptides, such as the adenovirus ElA proteins (14,26,56) and the herpes simplex virus ICP4, ICP5, and ICP8 proteins (5,7,47,49), no selective enrichment of origin DNA fragments was reported.…”

Papillomavirus polypeptides E6 and E7 are zinc-binding proteins

“…Interestingly, both Ela and the HPV-16 E7 proteins have also been found to transactivate the adenovirus E2 promoter and share a region of limited homology upstream of the Cys-X-X-Cys motifs (14). Although these similarities between E7 and Ela may suggest a similar mechanisms of action, a potential difficulty with this hypothesis is data indicating that E7 is a cytoplasmic protein (21) while Ela is a nuclear protein (18). Therefore, more studies are required for a better understanding of the basis of their similar activities.…”