Unusual suppression properties of lysogens containing derivatives of phi 80 psu3+

Nonsense codon suppressing lysogens of E. coli have been made using phi 80 psu3+-A2 and phi 80 psuoc+-A2, heat-sensitive amber and ochre suppressing derivatives, respectively, of bacteriophage phi 80. The various lysogens selected differ in strength of suppression as well as in heat sensitivity of suppressor function. Heat-resistant derivatives, some still carrying the A2 mutation, can be selected from the heat sensitive parents. Mapping experiments indicate that the phi 80 derivatives integrate at the tyrTV locus, which contains two copies of tRNA1Tyr. The origin of the various suppressor phenotypes appears to be related to the great variety of distinctive recombination events possible either between the incoming tRNA1Tyr gene and the host copies, or among the three copies of this gene in the lysogens.