Newly isolated temperature‐sensitive cdc35 mutants of Saccharomyces cerevisiae have been characterized. They show the morphology, growth and conjugation characteristics typical of class‐A or class‐II start mutants. The cdc35 mutation induces a significant decrease of the intracellular cAMP level and produces a thermolabile adenylate cyclase. By classical genetic criteria the CDC35 gene is identical with the structural gene of adenylate cyclase, CYR1. The results of the mutant selection, the kinetics of macromolecule accumulation and the cell‐density change of cdc35 mutants at the restrictive temperature, indicate that CDC35 function may not be cell cycle‐specific. A new mutation, cas1, was isolated and partially characterized. It mediates the suppression by external cAMP of the unlinked cdc35 mutation. It causes a slight increase of the intracellular cAMP level and has strong effects on the adenylate cyclase activities, especially on the Mg2+ dependent activity. The data suggest that the CAS1 protein is a controlling element of adenylated cyclase. The CAS1 locus is different from the RAS1 and RAS2 loci.
The ERG10 gene specific to S. uvarum, a brewing yeast, has been cloned by complementation of an S. cerevisiae erg10 mutant. S. uvarum contains two different ERG10 genes. One of these is similar to the S. cerevisiae ERG10 gene; they are structurally different, but functionally homologous. The cloned ERG10 gene has been located on chromosome XVI, and we have shown that it is allelic to the previously isolated tsm0115 mutants. Northern blot and sequence analysis indicate that the ERG10 gene is highly expressed, and biochemical and genetic evidence show that it encodes the cytoplasmic acetoacetyl CoA thiolase.
The current yeast map has 16 chromosomes, each originally defined by a centromere-linked gene unlinked to previously defined centromere markers. We examined four genes, cly2, KRB1, AMY2, and tsm0115, each centromere linked, but previously thought to be not on chromosomes I to XVI. We found that AMY2 is linked to cly2, and both are on chromosome II. tsm0115 is on the left arm of chromosome XVI. We confirm the earlier evidence that KRB1 is not on chromosomes I through XVI. This gene thus defines a new chromosome XVII. We also report meiotic linkage of met4 and pet8 (on chromosome XIV), confirming the connection between the petx-kex2 fragment of XIV and the centromere of XIV.
Chromosomal DNA molecules of Saccharomyces uvarum and Saccharomyces cerevisiae were separated using Orthogonal Field Alteration Gel Electrophoresis (OFAGE). Hybridization with specific probes of S. cerevisiae chromosomes allowed the identification of seven chromosomes of S. uvarum. The majority of the studied chromosomal DNA molecules show the same OFAGE mobility as the corresponding molecules of S. cerevisiae, with some minor differences.
Hybridizations with two distinct bands of S. uvarum were observed with each URA1 (marker of chromosome XI) and ARG80 (marker of chromosome XIII) probes, demonstrating the presence of at least two copies of these genes in the brewing yeast.
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