Transcription and sequence studies of a 4.3-kbp fragment from a ds-DNA eukaryotic algal virus.

A 4.3-kbp portion of the genome from the Chlorella virus, PBCV-1, has been cloned and sequenced. Minimally, five open reading frames (ORFs) were identified on this fragment. Transcriptional analysis indicates that each ORF encodes complex patterns of RNA. The total length of transcribed RNA exceeds that of the ORF indicating either post-transcriptional modification or multiple transcriptional start/stop sites. The sequence TTTTTNT, previously described as the transcriptional stop site for the early genes of vaccinia virus, is also found downstream of each of our ORFs. The regions 5' to each ORF were very A + T-rich (approx 80%) but distinct promoter sequences were not unambiguously identified.