An element downstream of the transcription start site is required for activation of Bombyx mori nucleopolyhedrovirus bro-c promoter.
Bombyx mori nucleopolyhedrovirus (BmNPV) contains five baculovirus repeated ORF (bro) genes. We have previously reported that all of these genes (bro-a, b, c, d and e) are transcribed as early genes and require viral factor(s) for their expression. In this study, we investigated the mechanism of promoter activation of the bro-c gene. Transient expression assays using genomic libraries of BmNPV indicated that the baculoviral trans-regulator IE-1 is responsible for activating the bro-c promoter. To identify essential site(s) for promoter activation, mutations were introduced to the promoter region of bro-c. Interestingly, it was shown that the pentanucleotide sequence CACGC located 30 nucleotides downstream of the RNA start site was essential for bro-c promoter activation. In addition, the RNA start site and the spacing between the RNA start site and CACGC were also required for promoter activation. By introducing a CACGC sequence into the corresponding region of the bro-b promoter, which is not normally trans-activated by IE-1, we demonstrated that this pentanucleotide motif has the ability to confer trans-activation by IE-1 on a promoter. Gel retardation experiments also showed a sequence-specific DNA binding protein induced by baculovirus infection interacts with the CACGC motif.
Suzuki
M G
MG
Laboratory of Molecular Entomology and Baculovirology, RIKEN, Wako, Japan.
Kang
W K
WK
Maeda
S
S
D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000821:virology*; D005786:Gene Expression Regulation; D005821:Genetic Techniques; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D009154:Mutation; D017924:Nucleopolyhedroviruses / Q000235:genetics*; D016366:Open Reading Frames; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D015534:Trans-Activators / Q000502:physiology; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000502:physiology*
D015534:Trans-Activators; D014764:Viral Proteins