Transcription elongation activity of the vaccinia virus J3 protein in vivo is independent of poly(A) polymerase stimulation.
Prior genetic analysis suggests that the vaccinia virus J3 gene product, previously characterized as a bifunctional (nucleoside-2'-O-)-methyltransferase and poly(A) polymerase stimulatory factor, is a postreplicative positive transcription elongation factor. To test this hypothesis, viruses bearing mutations in the J3 gene were characterized with respect to viral protein and RNA synthesis in infected cells. The analysis reveals that compared to wt virus infections, J3 mutants synthesize reduced amounts of large late viral proteins and shorter-than-normal intermediate and late mRNAs. Structural analysis of one late mRNA shows that it is specifically truncated from the 3' end, thus accounting for its shorter than normal chain length. Thus J3 mutant viruses are defective in elongation of transcription of postreplicative viral genes, strongly suggesting that the J3 gene product normally acts as a positive transcription elongation factor. Biochemical analysis of one J3 missense mutant demonstrates that it retains poly(A) stimulatory activity but is defective in (nucleoside-2'-O-)-methyltransferase activity. Thus the elongation factor activity of the J3 gene product is independent of the poly(A) stimulatory activity. It remains to be determined whether the (nucleoside-2'-O-)-methyltransferase and elongation factor activities of the J3 protein are linked or can be uncoupled by mutation.
Xiang
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Y
Department of Molecular Genetics, Center for Mammalian Genetics, University of Florida, Gainesville, Florida, 32610-0266, USA.
Latner
D R
DR
Niles
E G
EG
Condit
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RC
D000818:Animals; D002522:Chlorocebus aethiops; D004591:Electrophoresis, Polyacrylamide Gel; D006639:Histidine / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D011061:Poly A / Q000378:metabolism; D011062:Polynucleotide Adenylyltransferase / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D014616:Vaccinia virus / Q000235:genetics / Q000378:metabolism*; D014709:Vero Cells
C407246:J3 protein, Vaccinia virus; D014157:Transcription Factors; D011061:Poly A; D006639:Histidine; D011062:Polynucleotide Adenylyltransferase