Nucleotide sequence and transcription of the right early region of bacteriophage PRD1

We have sequenced the rightmost 1,700 base pairs of bacteriophage PRD1. This region encompasses the right early region and completes the sequence of all PRD1 early functions. We have also mapped the 5' initiation site of right early transcripts in vivo and in vitro. This has allowed us to assign gene XII to an open reading frame and suggests that another open reading frame may also be expressed. Gene XII, which has been implicated in the replication process and the regulation of gene expression, is predicted to encode a protein with a molecular mass of 16.7 kilodaltons. Data base searches have revealed no significant homology between the product of this gene and other proteins. Transcription mapping studies have revealed that right early transcripts elongate from right to left and have enabled us to identify the right early promoter. This promoter behaves identically in vivo and in vitro. We also demonstrate that this promoter directs the transcription of two RNAs of different sizes in vitro.