Type 1 protein phosphatase acts in opposition to IpL1 protein kinase in regulating yeast chromosome segregation.

Abstract

The IPL1 gene is required for high-fidelity chromosome segregation in the budding yeast Saccharomyces cerevisiae. Conditional ipl1ts mutants missegregate chromosomes severely at 37 degrees C. Here, we report that IPL1 encodes an essential putative protein kinase whose function is required during the later part of each cell cycle. At 26 degrees C, the permissive growth temperature, ipl1 mutant cells are defective in the recovery from a transient G2/M-phase arrest caused by the antimicrotubule drug nocodazole. In an effort to identify additional gene products that participate with the Ipl1 protein kinase in regulating chromosome segregation in yeast, a truncated version of the previously identified DIS2S1/GLC7 gene was isolated as a dosage-dependent suppressor of ipl1ts mutations. DIS2S1/GLC7 is predicted to encode a catalytic subunit (PP1C) of type 1 protein phosphatase. Overexpression of the full-length DIS2S1/GLC7 gene results in chromosome missegregation in wild-type cells and exacerbates the mutant phenotype in ipl1 cells. In addition, the glc7-1 mutation can partially suppress the ipl1-1 mutation. These results suggest that type 1 protein phosphatase acts in opposition to the Ipl1 protein kinase in vivo to ensure the high fidelity of chromosome segregation.

A putative serine/threonine kinase encoding gene BTAK on chromosome 20q13 is amplified and overexpressed in human breast cancer cell lines

“…In this paper we describe isolation, by direct selection, of a partial cDNA sequence for a putative serine/threnonine kinase encoding gene harbored on chromosome 20q13 that is ampli®ed and overexpressed in human breast cancer cell lines. This novel gene being called BTAK (Breast Tumor Ampli®ed Kinase) shares signi®cant homology with the kinase domains of yeast and Drosophila kinase known to be involved in chromosome segregation (Francisco et al, 1994;Glover et al, 1995). BTAK gene maps close to the region on 20q amplicon that has been associated with aggressive breast cancer.…”

Degradation of human Aurora2 protein kinase by the anaphase-promoting complex-ubiquitin-proteasome pathway

“…The yeast IPL1 and Drosophila aurora are required for chromosome segregation and centrosome maturation and constitute a family of serine/threonine kinases (Francisco et al, 1994;Glover et al, 1995). The IPL1 gene was identi®ed originally in a screen for yeast mutants that increase in ploidy (Francisco et al, 1994).…”

“…The IPL1 gene was identi®ed originally in a screen for yeast mutants that increase in ploidy (Francisco et al, 1994). The yeast IPL1 may regulate kinetochore function via phosphorylation of Ndc10p (Biggins et al, 1999).…”

Scd5p Mediates Phosphoregulation of Actin and Endocytosis by the Type 1 Phosphatase Glc7p in Yeast

“…The type 1 protein phosphatase (PP1) of Saccharomyces cerevisiae, Glc7p, has been shown to be involved in a diversity of cellular processes such as glycogen metabolism (Feng et al, 1991), translational control (Wek et al, 1992), glucose repression (Tu and Carlson, 1994), cell cycle progression (Hisamoto et al, 1994), and chromosome segregation (Francisco et al, 1994). The ability of Glc7p to perform such diverse functions stems presumably from its interactions with various targeting factors that direct the phosphatase to different substrates and/or sites of activity.…”