title: A common function for polyoma virus large-T and papillomavirus E1 proteins?
abstract: Nucleotide sequencing has revealed a common genetic organization for three papillomaviruses: BPV-1 (bovine papillomavirus type 1), HPV-1 (human papillomavirus type 1a) and HPV-6 (human papillomavirus type 6b). Several open reading frames, corresponding to as yet uncharacterized proteins, were observed in these genomes in the region that is required for oncogenic transformation by BPV-1 and for plasmidial maintenance of its genome. The longest of these frames, E1, is also the most conserved between the three viruses; we have compared the amino acid sequence of its putative product ('E1 protein') with those of the large-T proteins of three polyoma viruses and report here significant homologies in their carboxy-terminal halves, extending for over 200 amino acids. Moreover, similar secondary structures were predicted in this region, especially in two blocks of homologous residues, which correspond in the large-T proteins of polyoma and simian virus 40 (SV40) viruses to sites involved in the ATPase and nucleotide-binding activities. These observations suggest that the papillomavirus E1 proteins might have a function in common with the polyoma virus large-T proteins (which are required for the initiation of viral DNA replication). As it was suggested recently that the E1 gene product is involved in maintaining the BPV-1 genome as a plasmid in transformed cells, we speculate that the structural features conserved in these otherwise very different viruses are general characteristics of eukaryotic proteins involved in the control of DNA replication.
mesh_terms: D000595:Amino Acid Sequence; D000957:Antigens, Viral, Tumor / Q000235:genetics*; D004261:DNA Replication; D027383:Papillomaviridae / Q000235:genetics*; D011120:Polyomavirus / Q000235:genetics*; D011487:Protein Conformation; D014764:Viral Proteins / Q000235:genetics*; D014779:Virus Replication
chemical_list: D000957:Antigens, Viral, Tumor; D014764:Viral Proteins