Participation of hup gene product in replicative transposition of Mu phage in Escherichia coli

The closely related Escherichia coli genes hupA and hupB each encode a bacterial histone-like protein HU. We report here that mutator phage Mucts62 was unable to replicate in a hupA hupB double mutant, although it could replicate in hupA or hupB single mutant as efficiently as in the wild-type strain. Mucts62 was able to lysogenize the double mutant at 30 degrees C; cell killing occurred when the lysogen was incubated at 42 degrees C, but did not result in phage production. High-frequency non-replicative integration of Mu into host genomic DNA soon after infection could not be detected in the hupAB double mutant. These results provide the evidence that HU protein is essential for replicative transposition of Mu phage in E. coli, and also participates in high-frequency conservative integration.