Transcription mapping and functional analysis of the protein tyrosine/serine phosphatase (PTPase) gene of the Autographa californica nuclear polyhedrosis virus

Abstract

The protein tyrosine/serine phosphatase (PTPase) gene of the Autographa californica nuclear polyhedrosis virus yields two major transcripts of approximate sizes 3.1 and 3.9 kb. Both of these are very late transcripts, which accumulate to maximal levels more than 30 hr postinfection. The smaller transcript initiates at the T of an ATAAG sequence that lies 22 bp upstream of the putative start codon of the gene. The larger transcript initiates at the first A of a TTAAG sequence that lies approximately 798 bp further upstream. Thus, the larger transcript is made by transcribing through the entire hr1 region, which lies just 60 bp upstream of the putative translation start site. We have expressed the product of this gene as a fusion protein with glutathione-S-transferase and have shown that it has PTPase activity similar to that of the vaccinia virus H1 gene product: It dephosphorylates both protein phosphotyrosines and phosphoserines/phosphothreonines, and it is inhibited by vanadate, but not by okadaic acid.