The experiments described in this proposal are directed towards elucidation of the molecular mechanisms whereby adenovirus-infection disrupts cellular RNA metabolism. A detailed examination of newly-synthesized, cellular RNA sequences complementary to human tubulin and histone genes will be performed by saturation hybridization and size fractionation of both labelled and unlabelled RNA species. These experiments are designed to confirm our previous conclusion that transcription and enzymatic processing of cellular mRNA precursors is not inhibited in infected cells, even though newly synthesized, non-viral mRNA sequences fail to enter the cytoplasm. The packaging of these cellular sequences in ribonucleoprotein structures will also be examined during the late phase of infection. To establish whether discrimination between viral and cellular mRNA sequences occurs at this step of mRNA biogenesis. The role of potential trans- and cis-acting viral functions that might mediate selective appearance in the cytoplasm of adenoviral mRNA species will be investigated: certain conditional-lethal mutants with lesions in early regions E1A and E1B will be screened for failure to disrupt cellular metabolism and recombinants in which a selectable gene is placed under control of the adenovirus major late promoter site will be constructed for introduction into human cells, respectively. The unique properties of adenovirus-infected cells will also be exploited to provide a definitive test for transport of mRNA species from nucleic isolated by different procedures.