Showing papers on "Psychological repression published in 1983"

What is the function of nitrogen catabolite repression in Saccharomyces cerevisiae

Abstract: In contrast to the previously held notion that nitrogen catabolite repression is primarily responsible for the ability of yeast cells to use good nitrogen sources in preference to poor ones, we demonstrate that this ability is probably the result of other control mechanisms, such as metabolite compartmentation. We suggest that nitrogen repression is functionally a long-term adaptation to changes in the nutritional environment of yeast cells.

Transcription in vivo from SV40 early promoter deletion mutants without repression by large T antigen.

Abstract: Transfection of monkey cells with recombinant plasmids containing a beta-globin coding region fused to wild-type or deleted simian virus 40 (SV40) early region promoters has allowed an analysis of the transcriptional activity of these promoters in the absence of repression by large T antigen. We find that deletion of the TATA sequence does not reduce the transcriptional effectiveness of the promoter; however, the 5' ends of the transcripts are heterogeneous rather than being restricted to the usual sites. The short GC-rich repeat sequences between nucleotides 37 and 107 and the tandemly repeated 72-bp segment between nucleotides 107 and 250 are each essential for promoter function. The GC-rich repeats are functionally redundant and probably interchangeable, since several subsets of two or three of the GC-rich segments are sufficient. One copy of the 72-bp sequence is sufficient to permit transcription. Moreover, the 72-bp repeat sequences function normally even if they are inverted relative to their normal orientation.

Effects of aerobic and anaerobic shock on catabolite repression in cyclic AMP suppressor mutants of Escherichia coli.

Abstract: Cultures of Escherichia coli K-12 grown on glucose or gluconate under aerobic conditions exhibited catabolite repression of beta-galactosidase synthesis. Depression occurred when these cultures were subjected to anaerobic shock. These states of repression and depression were found to be associated with low and high differential rates of cyclic AMP synthesis, respectively. This observation is consistent with the view that cyclic AMP plays a central role in the catabolite repression phenomenon. We report here, however, that identical stages of repression and derepression occur in mutant strains possessing cya crp(Csm) genotypes and therefore unable to synthesize cyclic AMP. These results suggest that cyclic AMP is not the sole regulator involved in catabolite repression.

Catabolite repression and nitrogen control of allantoin-degrading enzymes in Pseudomonas aeruginosa

Abstract: The formation of the allantoin-degrading enzymes allantoinase, allantoicase and ureidoglycolase in Pseudomonas aeruginosa was found to be regulated by induction, catabolite repression and nitrogen control. Induction was observed when urate, allantoin or allantoate were included in the growth medium, but not with ureidoglycolate. Tricarboxylic acid cycle intermediates exerted catabolite repression of the synthesis of the three enzymes, while pyruvate and glucose caused less repression. The operation of a nitrogen control mechanism in the regulation of the allantoin-degrading enzymes could be demonstrated with glutamine synthetase-negative mutants, which showed elevated synthesis and escape from catabolite repression when growth was limited for glutamine.

Multiple regulation involved in the expression of the uxuR regulatory gene in Escherichia coli K-12.

Abstract: We have isolated a strain carrying a fusion of the beta-galactosidase structural gene to the promoter of the uxuR regulatory gene with the aid of the Casadaban Mud (Aprlac) phage. Analysis of mutants with deletions that were derived from the uxuR::Mud1 insertion strain confirmed the counterclockwise transcription direction of the uxuR gene. The uxuR-lacZ fusion strain was also used to examine the regulation of expression from the uxuR promoter. It was observed that an increase in the copy number of the uxuR gene results in an increased repression of beta-galactosidase synthesis. Overproduction of the exuR repressor also caused a decrease of the beta-galactosidase level. In all cases, the repression of beta-galactosidase synthesis was accompanied by a stronger repression of uxuB gene product synthesis. These results indicate that the expression of the uxuR gene is repressed by its own product but also by the exuR repressor. The different types of regulation of the two uxu operons are thus identical.

Regulation of nitrogen catabolic enzymes in Vibrio alginolyticus

Abstract: Repression by ammonia of enzyme systems responsible for the utilization of other nitrogen-containing compounds is known as nitrogen catabolite repression or end-product repression, and has been shown to be a control mechanism in Gram-negative organisms such as Escherichia coli, Klebsiella aerogenes, and Salmonella typhimurium [1,2], yeasts [3] and fungi [4]. However, the inducible nitrogen catabolic enzymes, arginase, alanine dehydrogenase and histidase in Gram-positive Bacillus strains are not regulated by nitrogen catabolite repression [5,6]. Although Vibrio alginolyticus is a Gram-negative bacterium, it is similar to Gram-positive Bacillus strains in a number of respects: they produce true extracellular proteases during the stationary growth phase [7-10]; protease production is rifampin-insensitive [11-13] and is subject to endproduct and catabolite repression which is not relieved by cAMP [9,10,14,15]. In Bacillus subtilis and V. alginolyticus, histidine is the inducer of the Hut enzymes [16,17] whereas in E. coli, K. aerogenes and S. typhimurium urocanic acid is the inducer of the Hut operon [18-20]. Since aspects of enzyme regulation in V. alginolyticus resemble those found in Bacillus strains rather than in the more closely related Gram-negative strains, we investigated the phenomenon of nitrogen catabolite repression in V. alginolyticus.