DELETION ANALYSIS OF THE PROMOTER FOR THE CUCUMBER NECROSIS VIRUS 0.9-KB SUBGENOMIC RNA

Sequences comprising the core promoter for the cucumber necrosis virus (CNV) 0.9-kb subgenomic RNA have been determined using deletion analy sis and site-directed mutagenesis. The deletion studies indicate that the promoter lies within a region located 20 nucleotides upstream and 6 nucleotides downstream and including the subgenomic start site. Sequ ences further upstream or downstream of the core promoter do not appea r to strongly affect promoter activity or viral RNA accumulation. Resu lts of site-directed mutagenesis studies indicate that nucleotides imm ediately surrounding the subgenomic start site regulate promoter activ ity. Comparison of sequences within the CNV promoter region with the c orresponding region of other tombusviruses shows that the tombusvirus promoter shares a region of near complete identity in 14 of the 26 cor e promoter nucleotides. Little similarity exists between the CNV 0.9-k b subgenomic RNA promoter and the region surrounding the transcription initiation site for the CNV 2.1-kb subgenomic RNA. Likewise, limited similarity occurs with the 5' region of CNV genomic RNA. Sequences sim ilar to the ICR2-like motifs found in the promoters of several alphavi rus-like (supergroup III) plant and animal viruses are not apparent Th is study represents the first analysis of a subgenomic promoter from a member of supergroup II of positive-strand RNA viruses. (C) 1995 Acad emic Press, Inc.