The transcription termination site at the end of the early region of bacteriophage T7 DNA.

The nucleotide sequence through the transcription termination site for Escherichia coli RNA polymerase at the end of the early region of T7 DNA has been determined. RNA chains terminate at adjacent residues in the DNA sequence: about 2/3 of the chains end in C and 1/3 in G. A potential stem and loop structure, containing a stem of eight uninterrupted base pairs and a four-base loop, is centered 17-18 bases ahead of the chain termini. Transcription by E. coli RNA polymerase terminates efficiently at this site in vivo and in vitro, but transcription by T7 RNA polymerase is essentially unaffected. There are no primary cleavage sites for RNase III near the transcription termination site. The site of termination lies within HpaI fragment Q of T7 DNA, whose entire 446-nucleotide long sequence was determined. Cleavage sites for other restriction endonucleases are located conveniently for manipulating the DNA sequence around the termination site. The coding sequence for the last 82 amino acids of the T7 DNA ligase protein was identified, as was the beginning of a coding sequence for a possible late T7 protein from beyond the termination site.