Bacteriophage T4 late promoters: mapping 5' ends of T4 gene 23 mRNAs.

More than thirty 5' ends of RNA molecules which transverse the bacteriophage T4 late gene, gene 23, have been mapped by nuclease protection and reverse transcription, to a 1.7 kilobase pair (kbp) region upstream of gene 23. Most of these 5' ends arise from RNA processing and degradation. Two sites at which RNA synthesis is initiated have been identified by guanylylation of diphosphate- or triphosphate-terminated RNA with vaccinia virion "capping" enzyme and are situated approximately 0.1 and 0.9 kbp upstream of gene 23. At least one other promoter lies more than 1.7 kbp upstream of gene 23, that is, outside of the mapped region.