Vaccinia virus capping enzyme is a transcription initiation factor.
It has previously been demonstrated that vaccinia virus capping enzyme is involved both in the formation of a 5' cap structure and in termination of early transcription. Here we show that capping enzyme has an additional activity which is required for transcription of intermediate genes. VITF-A and VITF-B have been defined as two activities which together with RNA polymerase are necessary and sufficient to transcribe intermediate genes in vitro. VITF-A and the viral capping enzyme are shown to copurify to near homogeneity. Direct evidence that capping enzyme is VITF-A was obtained by complementation of a reconstituted transcription system with viral capping enzyme expressed in Escherichia coli. Although capping enzyme is a cofactor in early transcription termination, intermediate transcription is not terminated in response to the early termination signal. Capping enzyme is shown to form a complex with RNA polymerase in the absence of VITF-B. This appears to be a prerequisite for the formation of a stable initiation complex.
Vos
J C
JC
European Molecular Biology Laboratory, Gene Expression Program, Heidelberg, FRG.
Sasker
M
M
Stunnenberg
H G
HG
D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008780:Methyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000302:isolation & purification / Q000378:metabolism*; D009713:Nucleotidyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D010957:Plasmids; D014157:Transcription Factors / Q000302:isolation & purification; D014158:Transcription, Genetic; D014616:Vaccinia virus / Q000201:enzymology*; D014764:Viral Proteins
D009097:Multienzyme Complexes; D014157:Transcription Factors; D014764:Viral Proteins; D008780:Methyltransferases; D009713:Nucleotidyltransferases; D012321:DNA-Directed RNA Polymerases; D010744:Phosphoric Monoester Hydrolases; C027731:capping enzyme, vaccinia virus