The UV sensitivity of some early-function temperature-sensitive mutants of phage T4

Abstract

Temperature-sensitive ( ts) mutants of phage T4 defective in ten early function genes were tested for sensitivity to ultraviolet (UV) light. The mutants were irradiated, plated on Escherichia coli S 6 , and incubated at various temperatures from 18 to 45°. UV sensitivity was shown by ts mutants defective in genes 30 (polynucleotide ligase), 32 (“joint former”), 41 (function unknown), 42 (deoxycytidylate hydroxymethylase), 43 (DNA polymerase), 44 (function unknown), 46 and 47 (deoxyribonucleases). Ts mutations in genes 45 (function unknown) and 56 (dCTP-dUTP nucleotidohydrolase) did not lead to UV sensitivity. The UV sensitivity of mutants defective in genes 30, 43, 46, and 47 is consistent with the model of DNA repair by excision. The observation that eight of ten early function genes contain UV-sensitive mutants is thought to reflect the complexity of the process of UV repair in T4-infected cells.