Functional Cooperation of Genes O and P

Abstract

Genes O and P are essential for autonomous replication of λ genomes. It is suggested that the O and P products are involved in the initiation of DNA synthesis since density-labeled susO or susP genomes undergo no detectable density shift after infection of su⁻ bacteria (Ogawa and Tomizawa, 1968).

Double mutants carrying an O gene expressing a temperature sensitive function (tsO) and a P gene expressing a suppressor dependent function (susP) were constructed, and suppressor independent revertants of the double mutants were isolated. The revertants from a double mutant with a particular combination of tsO and susP mutations were found to be temperature resistant in spite of the presence of the tsO gene. By further analysis of the phenomenon, functional cooperation of gene O and P is inferred.

MATERIALS AND METHODS
Bacteria used were C600suII⁺ (Appleyard, 1954), YmelsuIII⁺ (Yanofsky, and Ito, 1966, from A. Goldberg), CR63suI+λ^s, a spontaneous mutant isolated by T. Itoh from CR63 (Appleyard et al., 1956), C600uvrA54 (from A. Miura) and 594su⁻ (from J. Weigle). The sus mutants used were O8, P3 (Campbell, 1961) and P207 (Thomas, 1966). The order of the mutant loci is 08-P3-P207. Although C600suII⁺ and CR63suI⁺λ^s support the growth of all these sus mutants, YmelsuIII⁺ supports the growth of only susO8 and susP207. The insertion of a tyrosine residue as a result of translation of the P3 nonsense triplet by suppression in YmelsuIII⁺ may result in the production of an inactive P protein (Aono, 1970). Lambda tsO81 and tsP71 were selected from...