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Vaccinia virus capping enzyme is a transcription initiation factor.
Author(s) -
Vos J.C.,
Sasker M.,
Stunnenberg H.G.
Publication year - 1991
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1991.tb07795.x
Subject(s) - biology , vaccinia , virology , poxviridae , transcription factor , virus , transcription (linguistics) , genetics , gene , recombinant dna , linguistics , philosophy
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.