Presence in infected cells of nonvirion proteins encoded by adenovirus messenger RNAs of the major late transcription regions L0 and L1

The adenovirus major late promoter functions at early and intermediate times to produce a limited set of mRNAs that appear in the cytoplasm of productively infected HeLa cells. These mRNAs may be translated in cell-free systems to produce two unrelated polypeptides of approximately 13,500 Mr (L0-13.5K and L0-13.6K) and a pair of related polypeptides of approximately 55,000 Mr (the L1-52K/55K proteins). Radiochemical protein sequence analysis of in vitro synthesized proteins has identified the N-terminal sequences of the L0-13.5K and L0-13.6K proteins (J. B. Lewis and C. W. Anderson (1983), Virology 127, 112-123). Additional sequence analyses confirmed the identification of the open reading frame for the L0-13.5K protein, and identified the ATG encoded by nucleotides 11,040 to 11,042 from the left end of the adenovirus genome as the initial codon of the L1-52K/55K protein. Antisera raised against synthetic peptides homologous to these three amino termini were used to demonstrate the presence of the L0-13.5K protein, the L0-13.6K protein, and the L1-52K/55K proteins in extracts of HeLa cells infected by adenovirus 2. The L0-13.5K protein was detected at early, intermediate, and late times after infection. The L0-13.6K and L1-52K/55K proteins were detected only at late times. Immunofluorescence microscopy indicated that the L0-13.6K protein is distributed around the periphery of the nucleus and along fibers running the length of the cell. Nonpermeabilized infected cells were stained by anti-L0-13.6K peptide serum at a single spot on the cell surface. Neither the L0-13.6K nor the L1-52K/55K proteins were detected in purified virus.