Identification of a novel protein kinase that affects the chronological lifespan in fission yeast

Chronological lifespan is defined by how long a cell can survive in a non-dividing state. In yeast, it is measured by viability after entry into the stationary phase. To understand the regulatory mechanisms of chronological lifespan in Schizosaccharomyces pombe, it is necessary to identify and characterize novel factors involved in the regulation of chronological lifespan. To this end, we have screened for a long-lived mutant and identified that novel gene nnk1(+) that encodes an essential protein kinase is the determinant of chronological lifespan. We showed that the expression of major glucose transporter gene, ght5(+), is decreased in the isolated nnk1-35 mutant, suggesting that Nnk1 protein is involved in the regulation of ght5(+). The consumption of glucose in the growth medium after saturated growth was lower in the nnk1-35 mutant than that in wild-type cell. The isolated ght5 deletion mutant showed long-lived phenotype. Based on these results, we propose that Nnk1 regulates chronological lifespan through the regulation of ght5(+). Nnk1 might coordinate glucose availability and lifespan in fission yeast.