Proteins Involved in Phage Lambda Transcription Antitermination (Ribosome, Nus Genes, Rna Polymerase).

Bacteriophage (lamda) gene expression is dependent upon the ability of RNA polymerase to bypass transcriptional terminators at certain times during the phage life cycle. This ability is in turn dependent, in large measure, upon the action of the (lamda) N gene product, which is responsible for the modification of RNA polymerase to the termination-resistant state. In addition to N protein, the transcriptional antitermination reaction requires a phage nucleic acid locus called nut, and other protein factors provided by the E. coli host that are products of nus genes. Presented here is the analysis of two such nus genes, their protein products and interactions with other components of the system. Much of our underst and ing of the role of the host NusA protein in antitermination has come from the study of a hybrid bacterium in which the E. coli nusA gene has been replaced by the Salmonella analog. (lamda) does not grow on this hybrid host, but the isolation of a phage mutant that does grow led to the identification of a NusA protein recognition site within the nut region (boxA). It is shown here that (lamda) must have at least two mutations in the N gene, in addition to the alteration at boxA, to utilize the foreign NusA protein. Identification of the N mutations permitted construction of a new phage mutant that carries only the boxA alteration; analysis of its phenotype is presented. To further underst and the interactions among N, boxA, and NusA, the Salmonella nusA gene was cloned and sequenced. Potential protein contact points are proposed. Analysis of another host factor, NusE, is also presented. It is shown that nusE is the same as rpsJ, which codes for ribosomal protein S10. Several models to explain the participation of S10 are discussed; one suggests that the complete ribosome is directly involved in the (lamda) antitermination reaction. To test this hypothesis, a suppressor of the nusE mutation was selected and mapped to a large subunit ribosomal protein gene. These and other results are consistent with direct participation of the ribosome in the regulation of phage transcription.PhDGeneticsUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/160589/1/8512500.pd