Abstract
Calmodulin and its target enzymes are important regulators of numerous cellular processes, including reversible protein phosphorylation. The calmodulin-dependent protein phosphatase (calcineurin) has been suggested to play roles in activation of T cells and in the mating response of yeast. Recently, studies have shown it to be the target of immunosuppressant drugs such as cyclosporin and FK-506. In this study, we have cloned the gene for the catalytic subunit of calcineurin, CnA, from the yeast Schizosaccharomyces pombe. The gene (named ppb1+) has been mapped to chromosome II by analysis of the hybridization of a genomic DNA probe to an ordered library. The gene produces a single mRNA species of 2.5 kilobases, which varies during the cell cycle in exponentially growing cells. In addition, expression of ppb1+ mRA is induced by nitrogen starvation, a condition that favors mating in S. pombe. The ppb1+ gene promoter contains a cis-acting element for the ste11 transcription factor, and we have shown that induction of the ppb1+ mRNA during nitrogen starvation is dependent on the ste11 gene product. Together with earlier studies showing that disruption of the ppb1+ gene in S. pombe results in sterility (Yoshida, T., Toda, T., and Yanagida, M. (1994) J. Cell Sci., 107, 1725-1735), our studies suggest that the ppb1+ gene plays a role in the gene expression cascade that is essential for mating and sporulation in S. pombe.
Highlights
Calmodulin and its target enzymes are important regulators of numerous cellular processes, including reversible protein phosphorylation
Cell Sci., 107, 1725–1735), our studies suggest that the ppb1؉ gene plays a role in the gene expression cascade that is essential for mating and sporulation in S. pombe
In Aspergillus nidulans, a filamentous fungus related to yeast, we have shown that the CnA gene is essential for proliferation and that the mRNA is expressed in a cell cycle-dependent manner (2)
Summary
CaM, calmodulin; CnA, calcineurin A; X-Gal, 5-bromo-4-chloro-3-indoyl -D-galactoside; PCR, polymerase chain reaction; bp, base pair(s); kb, kilobase(s). Protein phosphatase, calcineurin, has recently been suggested to play important roles in the control of cell growth and division (2, 3), regulation of gene expression (4, 5), and in response to mating pheromone in the yeast Saccharomyces cerevisiae (6, 7). In Aspergillus nidulans, a filamentous fungus related to yeast, we have shown that the CnA gene is essential for proliferation and that the mRNA is expressed in a cell cycle-dependent manner (2). In the yeast S. cerevisiae, multiple CnA genes exist, and while it appears they are not essential for vegetative growth, this enzyme appears to play a role in the mating pheromone response pathway (6, 7). Our studies show that CnA expression during nitrogen starvation is directly dependent on ste11ϩ and suggests that CnA may be an integral component of the signal transduction mechanism that functions during the mating response in yeast
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