DNA-binding Proteins specific for Cells infected by Adenovirus

Abstract

DURING productive infection of human cells with types 2 or 5 adenovirus a number of proteins specific for the infected cells, but not found in the intact virion, can be detected by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate (SDS)_{1, 2}. None of these proteins, however, has been isolated in a native state and therefore their functions remain obscure. The observation that replicating adenovirus DNA contained extensive single stranded regions (refs 3, 4, and U. Petterson, personal communication) led us to look for proteins specific for infected cells that bind only to single stranded DNA and may be involved directly in DNA replication. Such a class of proteins, originally described by Alberts and Frey⁵, has now been found in a number of prokaryotic systems^5–7 as well as in mammalian cells^{8, 9}, and they are known, at least in the case of T4 gene 32 protein, to be required for DNA replication and genetic recombination⁵. To eliminate the large excess of adenovirus coat proteins, synthesised in human cells, which are known to bind to DNA¹⁰, we used African green monkey cells as hosts. In these cells viral DNA synthesis occurs at a normal rate but late viral capsid proteins are not produced or are synthesised in very small amounts¹¹.