Selective effects on adenovirus late gene expression of deleting the E1b 55K protein.

The E1b gene of human adenovirus 5 (Ad5) encodes a 55K product previously shown to be required for the efficient accumulation of mRNAs derived from the major late primary transcript in the cytoplasm of infected cells. This finding is extended here to include the transcripts from other viral promoters activated during the late phase of infection. Conversely, accumulation of mRNA derived from the major late promoter at early times is not dependent on this E1b function. Cytoplasmic levels of the various differentially spliced products of the major late unit are not equally dependent on the E1b 55K protein. Rather, the longest mRNA species within each 3'-coterminal family shows the greatest dependence. These findings support a model in which the Ad5 E1b 55K protein acts to facilitate the movement of mature viral mRNA away from the nuclear matrix of the infected cell.