A 30-KDA HOST PROTEIN BINDS TO 2 VERY-LATE BACULOVIRUS PROMOTERS

A 30-kDa host factor (polyhedrin-promoter-binding protein; PPBP) speci fically binds to sequences critical for transcription from the baculov irus polyhedrin (p29) gene initiator promoter [Burma, S., Mukherjee, B ., Jain, A., Habib, S. & Hasnain, S. E. (1994) J. Biol. Chem. 269, 275 0-2757; Mukherjee, B., Burma, S. & Hasnain, S. E. (1995) J. Biol, Chem 270, 4405-4411]. A host factor also binds, in gel shift assays, to th e very-late p10 gene promoter through DNA sequence motifs similar to t he PPBP . p29 interaction. The p10 . host factor complex was specifica lly competed out with oligonucleotides containing p29 cognate sequence motifs AATAAA and TAAGTATT, but this did not occur when these motifs were replaced with random sequences. From ultraviolet cross-linking an alysis, the molecular mass of this host factor was estimated to be app roximately 30 kDa. Experiments were performed to investigate if this h ost factor displayed any differences in affinity and turnover with res pect to the p29 and p10 untranslated leader sequences known to be impo rtant for temporal fine toning and the late burst of transcription. Ha lf-life determination of the p10-binding protein revealed similar bind ing affinities for the initiator elements of both the promoters, but h igher affinity for the p10 5'-untranslated region (approximate to 30 m in versus approximate to 10 min). The involvement of a similar host fa ctor binding to both the p10 and p29 promoters indicates the possibili ty of a similar mode of transcription initiation from these two very-l ate promoters.