Defining a bacteriophage T4 late promoter: absence of a "-35" region.

We performed a deletion analysis to identify the minimal DNA sequence required for the function of the T4 late promoter, P23. A minipromoter derivative of P23 was constructed, containing 35 bp of T4 DNA from -18 to +17 with respect to the transcriptional initiation site. This derivative retains the TATAAATA homology and is competent to serve as a T4 late promoter both in vitro and in vivo. Its transcriptional activity in vivo is regulated identically to a wild-type plasmid-borne P23, requiring the function of T4 genes essential for late transcription, but not requiring T4 DNA replication. Recombination with the T4 phage chromosome is not significant for mini-P23 activity in vivo.