Novel Sp family-like transcription factors are present in adult insect cells and are involved in transcription from the polyhedrin gene initiator promoter

We earlier documented the involvement of a cellular factor, polyhedrin (pol h) promoter-binding protein, in transcription from the Autographa californi ca nuclear polyhedrosis virus polh gene promoter. Sequences upstream of the polh promoter were found to influence polh promoter-driven transcription. Analysis of one such region, which could partially compensate for the mutat ed polh promoter and also activate transcription from the wild-type promote r, revealed a sequence (AcSp) containing a CACCC motif and a loose GC box r esembling the binding motifs of the transcription factor Sp1, AcSp and the consensus Spl sequence (cSp) specifically bound factor(s) in HeLa and Spodo ptera frugiperda (Sf9) insect cell nuclear extracts to generate identical b inding patterns, indicating the similar nature of the factor(s) interacting with these sequences. The AcSp and cSp oligonucleotides enhanced in vivo e xpression of a polh promoter-driven luciferase gene. In vivo mopping of the se factor(s) significantly reduced transcription from the polh promoter. Re combinant viruses carrying deletions in the upstream AcSp sequence confirme d the requirement of these factor(s) in polh promoter-driven transcription in the viral context. We demonstrate for the first time DNA-protein interac tions involving novel members of the Sp family of proteins in adult insect cells and their involvement in transcription from the polh promoter.