SOME PROPERTIES OF HU ARE MODIFIED AFTER THE INFECTION OF ESCHERICHIA-COLI BY BACTERIOPHAGE-T4

Escherichia coli HU, an abundant, nucleoid-associated, DNA-binding pro tein, plays a role in several biological processes including DNA repli cation. Many other bacteria have well-conserved HU homologs, and there are several more-distantly related members of the family, including T F1, encoded by Bacillus subtilis phage SPO1. We have asked whether col iphage T4 like SPO1, encodes an HU homolog or whether it alters the pr operties of host HU. We have been unable to detect a T4-specified HU h omolog, but we have shown that E. coli HU extracted from phage-infecte d cells differs in some properties from that extracted from uninfected cells. First, HU from uninfected cells inhibits a reconstituted T4 DN A replication system, whereas HU from infected cells does not. Second, HU from infected cells appears to bind a T4-encoded polypeptide as sh own by coimmunoprecipitation. We propose that such binding alters HU f unction in T4-infected cells.