Cloning and characterization of NSP1, a locus encoding a component of a CDC25-dependent, nutrient-responsive pathway in Saccharomyces cerevisiae.

The NSP1 gene in Saccharomyces cerevisiae has been identified by its ability, when expressed at high levels, to bypass the CDC25 requirement for growth. Sequence analysis of the cloned NSP1 locus suggests that the NSP1 product contains 269 amino acids and has a membrane-spanning domain at its carboxyl terminus. The NSP1 protein does not have sequence similarity to other known proteins, and is not related to the CDC25 protein, or to any of the previously described suppressors of CDC25 mutants. Phosphoprotein analysis of NSP1-suppressed cells indicates that the NSP1 product controls the phosphorylation of two 31 kD proteins whose phosphorylation and dephosphorylation are strongly correlated with cell-cycle arrest and proliferation, respectively, and suggests that the NSP1 product is an important downstream element of a CDC25-dependent, nutrient-responsive, phosphorylation pathway.