Cooperative effects of bacterial mutations affecting λ N gene expression

Abstract

We report the isolation and initial characterization of a class of mutations, Snu, that map near the rif locus on the Escherichia coli chromosome. Snu mutations inhibit the growth of phage A, an effect primarily seen when Snu mutations are combined with another class of mutations, nus. Nus mutations have previously been shown to inhibit the expression of the N gene product of h, and the experiments reported here suggest that Snu mutations add to this inhibitory effect. One Snu mutation, Snu-9, was shown to cause bacterial growth to be temperaturesensitive. This suggests that, at least, some Snu mutations may be in genes coding for a function essential for bacterial growth. Since genes coding for the p and p' subunits of RNA polymerase map in this region, we recognize that Snu mutations might alter either of these subunits of RNA polymerase. Complementation studies demonstrate that Snu+ is dominant to Snu, indicating that the mutant phenotype is due to the partial loss of a function necessary for full N expression. Although the hosts carrying Snu and nus mutations (called Supernus) severely restrict the growth of phage which express the N function of A, they do not show any increased inhibitory effect on the growth of himmP22 and Aimm21, phages which express N functions different from that of A. However, Supernus hosts do restrict the growth of a A variant that can grow well in bacteria carrying either component mutation, Snu or nus-. The restrictive effect of the Supernus strain is far greater than would be expected if the restriction was due to an additive effect of the two component mutations. This implies that there might be an interaction between Snu and nus products and that the Supernus phenotype results from an interference with this interaction. I Author to whom reprint requests should be ad-been identified, that being the p subunit of dressed.

Genetic interaction between the beta' subunit of RNA polymerase and the arginine-rich domain of Escherichia coli nusA protein

“…Reduced termination of transcription by nusAll or nusA10 is compensated for by rifampin-resistant p subunit mutations to some extent (22), and the snu mutation in rpoB accentuates the inhibitory effect of nusAl on K N antitermination (3). These results indicate functional interaction between RNA polymerase and NusA protein.…”

A mutation in the Escherichia coli rho gene that inhibits the N protein activity of phage λ

“…The nus mutations affect the RNA polymerase /3 subunit (nusC), L protein (nusA), ribosomal protein S10 (nusE), or a 14-kilodalton protein whose role in E. coli physiology is unknown (nusB). The nus mutations all block termination suppression by N (10)(11)(12)(13)(14)(15)(16). The nusA, nusB, and nusE mutations are most restrictive at 42°C.…”

Evidence that ribosomal protein S10 participates in control of transcription termination.

“…The nusC mutation has been located in the rpoB gene, which encodes the ,3 subunit of RNA polymerase. In addition to nusC, other mutations that map in the region of rpoB influence the activity of pN (30)(31)(32)(33). The location of a nus mutation in a gene encoding a ribosomal protein suggests a role for at least one ribosomal protein in the action of pN.…”