Interaction of satellite phage P4 with phage 186 helper

Abstract

Satellite phage P4 can utilize a derepressed 186 prophage as a helper for lytic growth. P4 requires all the 186 head, tail, and lysis genes, but none of the known 186 early genes. The P4 transactivation gene can replace the 186 B gene as a positive regulator of late gene expression. The ogr gene of P2 helper phage is the functional equivalent of the 186 B gene. A repressed 186 prophage does not support P4 growth, and thus P4 does not form plaques on a 186-lysogenic strain. Although P4 is able to derepress a P2 prophage helper ( E. W. Six and B. H. Lindquist, 1978, Virology 87, 217–230), it is unable to derepress a 186 prophage. Thus some repressible helper function may be required for P4 growth. Alternatively, 186 prophage may produce a P4 inhibitor.