The Rho Gene of E coli Maps at su A

Abstract

INTRODUCTION
The rho factor of Escherichia coli causes the termination of RNA transcription at specific sites on a variety of DNA templates (Roberts 1969; Richardson 1971; de Crombrugghe et al. 1973; Darlix 1974; Rosenberg, Weissman and de Crombrugghe 1975). These profound effects of rho activity in vitro suggest that rho plays a fundamental role in the control of in vivo gene expression. But the function of rho factor in the cell is not yet known, principally because no rho mutants have been identified. To facilitate the isolation of such mutants it would be helpful to first map rho on the E. coli genome. In this paper I describe the results of such mapping experiments. While this work was in progress, Richardson, Grimley and Lowery (1975) showed that an abnormal rho activity is present in E. coli strains mutant at the su A locus, a gene involved in the translational polarity of nonsense mutations. Using an independent criterion for the localization of the rho gene, the experiments reported here show that the structural gene for rho is linked to su A. From these and other data (Richardson, Grimley and Lowery 1975; Ratner 1976) I conclude that the rho protein is the direct polypeptide product of the su A gene.

MATERIALS AND METHODS
Genetic Methods
Hfr matings were performed essentially as described by Miller (1972). The minimum time of mating needed to move the selected nutritional marker efficiently was determined in advance for each donor. Matings were interrupted by vortexing and 100-fold...