Identification of a cellular repressor of transcription of the adenoviral late IVa(2) gene that is unaltered in activity in infected cells.
The gene encoding the adenovirus type 2 IVa(2) protein, a sequence-specific activator of transcription from the viral major late promoter, is itself transcribed only during the late phase of infection. We previously identified a cellular protein (IVa(2)-RF) that binds specifically to an intragenic sequence of the IVa(2) transcription unit. We now report that precise substitutions within the IVa(2)-RF-binding site that decreased binding affinity increased the efficiency of IVa(2) transcription in in vitro reactions containing IVa(2)-RF. Consistent with the conclusion that this cellular protein represses IVa(2) transcription, mutations that led to more efficient transcription in the presence of IVa(2)-RF were without effect in reactions lacking this cellular protein. No change in the concentration or activity of IVa(2)-RF could be detected in adenovirus-infected cells during the period in which the IVa(2) gene is transcribed. We therefore propose that restriction of IVa(2) transcription to the late phase is the result of titration of this cellular repressor as the number of copies of the IVa(2) promoter increases upon replication of the viral genome.
Lin
H J
HJ
Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544-1014, USA.
Flint
S J
SJ
D000260:Adenoviruses, Human / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D004279:DNA, Viral / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
D004279:DNA, Viral; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors