Regulation of expression of the genome of bacteriophage M13. Gene V protein regulated translation of the mRNAs encoded by genes I, III, V and X.

With the aid of a binary plasmid in vivo testsystem it was demonstrated that the single-stranded DNA binding protein encoded by gene V of bacteriophage M13 not only regulates the synthesis of its cognate DNA replication proteins at the level of translation, but also of the assembly proteins and the coat proteins encoded by genes I and II, respectively. Furthermore, gene V protein functions as a translational autoregulator of its own synthesis. Comparison of the mRNA levels of genes I and X in the presence and absence of wild-type gene V protein indicated that gene V protein augments the physical stability of these mRNAs. The expression of the Escherichia coli beta-galactosidase gene and of a gene X mutant containing a deletion in the nontranslated mRNA leader sequence was not influenced by gene V protein, lending support to the conclusion that gene V protein exerts its regulatory effect via a specific nucleotide sequence in the leader sequences of the respective M13 mRNAs. We conclude that gene V protein functions as a master regulatory protein of the expression and replication of the M13 genome.