CHARACTERIZATION OF HOST-RANGE FACTOR 1 (HRF-1) EXPRESSION IN LYMANTRIA-DISPAR M NUCLEOPOLYHEDROVIRUS-INFECTED AND RECOMBINANT AUTOGRAPHA-CALIFORNICA M NUCLEOPOLYHEDROVIRUS-INFECTED IPLB-LD652Y CELLS

We previously identified a gene, host range factor 1 (hrf-1), in Lyman tria dispar M nucleopolyhedrovirus (LdMNPV) which promoted Autographa californica M nucleopolyhedrovirus (AcMNPV) replication in a nonpermis sive cell line IPLB-Ld652Y (Ld652Y). A recombinant AcMNPV, vAcLdPS, th at bore hrf-1 controlled by two synthetic baculovirus late promoters a nd that replicated in Ld652Y cells was constructed. In this study, we constructed a new recombinant AcMNPV, vAcLdPD, bearing only hrf-1 cont rolled by its own promoter. vAcLdPD replicated in Ld652Y cells in the same manner as vAcLdPS, confirming that hrf-1 alone was sufficient to promote AcMNPV replication in Ld652Y cells. hrf-1 was transcribed as a delayed early gene in LdMNPV but as an immediate early gene in both r ecombinant AcMNPVs. Primer extension analysis showed that the initiato r sequence TCAGT was used as the transcription start site in both LdMN PV and recombinant AcMNPVs. Additional sequencing revealed several reg ulatory motifs in the hrf-1 upstream region, hrf-1 transcripts in LdMN PV- and vAcLdPS-infected Ld652Y cells terminated near the polyadenylat ion signal at the end of hrf-1 ORF while in vAcLdPD, the hrf-1 transcr ipts terminated at a downstream polyadenylation signal at the end of O RF 603. Using Western blot analysis, we detected HRF-1 expression in b oth recombinant AcMNPV-infected Ld652Y cells but not in LdMNPV-infecte d Ld652Y cells. (C) 1997 Academic Press