Genetic analysis of a new mutation conferring cysteine auxotrophy in Saccharomyces cerevisiae: updating of the sulfur metabolism pathway

Article Abstract:

Genetic, phenotypic and enzymatic analyses were conducted on a new Saccharomyces cerevisiae cysteine auxotroph to elucidate the pathway of cysteine metabolism used by this organism. The results showed that this mutant is deficient in the gene coding for cystathionine gamma-lyase, designated STR1. Inactivation of STR1 leads to inactivation of the C4 to C3 transsulfuration pathway, indicating that sulfur is incorporated in a C4 backbone and is exclusively synthesized from homocysteine. Based on the results, a modified pathway for sulfur amino acid biosynthesis is presented.

Physiological aspects, Microbial metabolism, Sulfur, Amino acids, Amino acid synthesis

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Isolation of crt mutants constitutive for transcription of the DNA damage inducible gene RNR3 in Saccharomyces cerevisiae

Article Abstract:

The genes coding for ribonucleotide reductase (RNR1, RNR2 and RNR3) are activated by DNA damage. Two hundred and two crt mutants transcribing the gene RNR3 in the absence of DNA damage were isolated through a general selection system using transcriptional fusion and reporter plasmids. Two hundred mutations are recessive and can be divided into nine complementation groups. Some groups also exhibit elevated RNR1 and RNR2 expression indicating a common pathway in the regulation of the three genes.

DNA repair, Genetic transcription, Transcription (Genetics)

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