The 5'-terminal ribonucleotide of an in vitro ColE1 transcript is not complementary to the DNA template.

A set of overlapping promoters in ColE1 DNA is identified using DNA and RNA sequencing methods. These promoters initiate a divergent pattern of in vitro transcription from a region near the colicin E1 promoter. A comparison of the 5'-terminal RNA sequences of the in vitro transcripts with the DNA sequence of the template indicates that one transcript initiates with a ribonucleotide (pppG) which is not complementary to the DNA template (a thymidylate residue is present on the coding strand at the designated transcription start point). A structural and functional counterpart for this phenomenon is suggested to exist near the opposite end of the colicin E1 gene.