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S Adhya

Publications and source records attributed to S Adhya.

At least 127 records · Page 7Linked to original sources
PubMed1978

Interaction of RNA polymerase and rho in transcription termination: coupled ATPase.

We have previously described temperature sensitive rho mutants of Escherichia coli (e.g., rho15) that are defective in transcription termination at various signals, including an IS2 DNA insertion in the gal operon [Das, A., Court, D. & Adhya, S. (1976) Proc. Natl. Acad. Sci. USA, 73, 1959-1963]. In this paper, we report the isolation of mutants altered in the beta subunit of RNA polymerase (a class of Rifampicin-resistant mutants), which restore gal IS2 polarity in the rho 15 strain. It has been shown that one of these suppressor RNA polymerases (rpoB101) requires rho to terminate transcription of phage lambda mRNA. In contrast to the wild type RNA polymerase, the suppressor RNA polymerase also terminates lambda mRNA transcription in the presence of rho15 protein. We have isolated new rho mutants (e.g., rho112) that are defective in transcription termination in the rpoB101 strain. These results strongly support the notion that rho and RNA polymerase interact functionally during transcription termination. We have shown that rho15 catalyzes ATP hydrolysis during transcription with rpoB101 RNA polymerase, but not with wild-type RNA polymerase. Because rho 15 protein hydrolyzes ATP in the presence of free RNA, we suggest that rho may recognize the 3'-OH end of RNA. During transcription, this recognition involves an interaction with RNA polymerase, resulting in the displacement of the polymerase and the release of the nascent mRNA.

Adenosine Triphosphatases↗
PubMed1977

Effect of undecanoic acid on germination of microconidia of wild and undecanoic acid resistance mutant of Trichophyton rubrum.

Effects of undecanoic acid (UDA) on germination of microconidia and elongation of germ tubes in UDA sensitive (udas) wild type Trichophyton rubrum and UDA resistant (udar) mutant derived from it, were studied. UDA inhibited conidial germination of udas and udar strains at 30 microgram/ml and 120 microgram/ml respectively which were minimum inhibitory concentrations of UDA for these two strains. When spores from both udas and udar were germinated in presence of subinhibitory concentration of UDA, germ tube growth was short. The elongation of germ tubes of spores pregerminated in absence of UDA was also inhibited by dose of UDA not sufficient to inhitib germination.

Drug Resistance, Microbial↗
PubMed1976

Isolation and characterization of conditional lethal mutants of Escherichia coli defective in transcription termination factor rho.

Polarity suppressor mutants that are conditional lethal for growth have been isolated in E. coli K12. The mutations map between the ilv and cya loci of the E. coli chromosome. Rho factor isolated from one of these ts mutants does not show transcription termination activity at any temperature tested; however, it is found to be temperature sensitive for its poly(C)-dependent ATPase activity. Unlike the previously known polarity suppressor mutants (suA and psu), the rho mutation suppresses all types of polarity. Other interesting properties of these mutants include ultraviolet sensitivity, recombination deficiency, and decreased ability to lysogenize temperate phages lambda and P1. Our results suggest that rho has an essential function in the growth and normal physiology of cells. The rho(ts) mutant allows the growth of phage lambda defective in the N gene. This result supports the model that N gene product prevents transcription termination by antagonizing rho activity.

Adenosine Triphosphatases↗
PubMed1976

Suppression of polarity of insertion mutations in the gal operon and N mutations in bacteriophage lambda.

Bacterial mutations (psuA and psu) known for their ability to suppress the polarity on nonsense mutations are shown to suppress the polarity of certain insertion mutations in the gal operon. The short insertion, IS1 (800 nucleotide pairs), is about 15 to 50% suppressed, whereas longer insertions, IS2 (1,400 nucleotide pairs), and IS3 (1,200 nucleotide pairs), are not. Some of the polarity suppressor mutations (psu-1, psu-2, and psu-3) are at least partially permissive for N-gene mutations (N7 and N53) of bacteriophage lambda, suggesting a relationship between natural and mutational polar signals. That this relationship may be complex is indicated by the fact that other suppressor mutations, effective in suppressing nonsense or insertion polarity, fail entirely to permit the growth of lambda N mutants.

Cell-Free System↗
PubMed1975

Selective effects of MgCl2 and temperature on the initiation of transcription at lac, gal, and lambda promoters.

We have studied the effect of Mg2+ on the formation of transcription preinitiation complexes (open complexes) at two adenosine 3':5'-monophosphate (cyclic AMP)-cyclic AMP receptor protein (CRP)-dependent promoters (lac and gal) and two phage lambda promoters, PL and PR. Mg2+ strongly interferes with open complex formation at the lac and gal promoters, partially inhibits the lambda PR promoter, and is without effect on the lambda PL promoter. Mutations in the lac and gal promoters can affect the response of the promoter to Mg2+. Cyclic AMP and CRP specifically reduce the inhibition of the lac and gal promoters by Mg2+. These factors also affect open complexes at lac and gal by (a) increasing the rate at which they are formed and (b) lowering the midpoint of the temperature transition curve for their formation by about 10 degrees. Open complexes at the lac promoter are more unstable to cooling, even in the presence of CRP and cyclic AMP, than open complexes at lambda promoters. Our studies suggest that the DNA of the lac and gal promoter regions is more resistant to denaturation than the DNA of phage promoter regions. Cyclic AMP and CRP act to decrease this stability, stimulating open complex formation under conditions unfavorable for DNA melting, e.g. low temperature and high Mg2+ concentrations.

Binding Sites↗
PubMed1974

Release of polarity in Escherichia coli by gene N of phage lambda: termination and antitermination of transcription.

The induction of lambda prophage provokes the constitutive expression of the adjacent gal operon in E. coli. This "escape synthesis" can result from transcription that initiates at a phage promoter and extends into the gal operon. The effect requires the product of the lambda gene N. N-mediated transcription not only fails to terminate at the prophage-bacterial junction and at the ends of bacterial operons, but ignores termination signals caused by polar insertions or ochre mutations within gal. Suppression of polarity by N-function is a cis-effect; only transcription initiated at the phage promoter is influenced. We propose that the transcription complex is influenced by N-product to become termination-resistant at a site in the phage genome (juggernaut model). This site appears to be at or near the phage promoter.

Chromosome Mapping↗