Prenylated Isoforms of Yeast Casein Kinase I, Including the Novel Yck3p, Suppress the gcs1 Blockage of Cell Proliferation from Stationary Phase

Abstract

The GCS1 gene of the budding yeast Saccharomyces cerevisiae mediate the resumption of cell proliferation from the starved, stationary-phase state. Here we identify yeast genes that, in increased dosages, overcome the growth defect of gcs1 delta mutant cells. Among these are YCK1 (CK12) and YCK2 (CKI1), encoding membrane-associated casein kinase I, and YCK3, encoding a novel casein kinase I isoform. Some Yck3p gene product was found associated with the plasma membrane, like Yck1p and Yck2p, but most confractionated with the nucleus, like another yeast casein kinase I isoform, Hrr25p. Genetic studies showed that YCK3 and HRR25 constitute an essential gene family and that Yck3p can weakly substitute for Yck1p-Yck2p. For gcs1 delta suppression, both a protein kinase domain and a C-terminal prenylation motif were shown to be necessary. An impairment in endocytosis was found for gcs1 delta mutant cells, which was alleviated by an increased YCK2 gene dosage. The ability of an increased casein kinase I gene dosage to suppress the effects caused by the absence of Gcs1p suggests that Gcs1p and Yck1p-Yck2p affect parallel pathways.

The Saccharomyces cerevisiae 60 S Ribosome Biogenesis Factor Tif6p Is Regulated by Hrr25p-mediated Phosphorylation

“…In S. cerevisiae there are four different isoforms of CK I, each encoded by a separate gene, YCK I, YCK 2, YCK 3, and HRR25 (12,(22)(23)(24). Among these isoforms, Hrr25p localizes throughout the cell (16), whereasYck1p, Yck2p, and Yck3p are prenylated and tightly bound to the plasma membrane (24,25). To show if any isoform of yeast CK I is able to phosphorylate Tif6p in vitro, we purified Hrr25p, Yck1p, and Yck2p and used these purified proteins to phosphorylate recombinant Tif6p (Fig.…”

A Novel Membrane-bound Glutathione S-Transferase Functions in the Stationary Phase of the Yeast Saccharomyces cerevisiae

“…The P1 fraction from JC104 cells was subjected to density gradient centrifugation as described previously (17,22). The resultant gradients were fractionated from top (fraction 1) to bottom (fraction 20) and assayed for HT-T7-Gtt1p and marker proteins by Western immunoblotting as described under "Experimental Procedures."…”

“…Subcellular Fractionation and Immunoblotting-JC104 cells were grown, lysed, and fractionated by differential centrifugation into 10,000 ϫ g pellet (P1), 170,000 ϫ g pellet (P2), and supernatant (S) fractions as described previously (17,22). P1 and P2 pellets were then subjected to density gradient fractionation (17).…”

The Yck2 Yeast Casein Kinase 1 Isoform Shows Cell Cycle-specific Localization to Sites of Polarized Growth and Is Required for Proper Septin Organization

“…The essential CK1 proteins encoded by the duplicate YCK1 and YCK2 genes are two of four Saccharomyces cerevisiae CK1 proteins (Hoekstra et al, 1991;Robinson et al, 1992;Wang et al, 1992Wang et al, , 1996. The Yck1 and Yck2 proteins are peripherally but tightly associated with the plasma membrane (Vancura et al, 1993(Vancura et al, , 1994 and carry a carboxy-terminal (C-terminal) -Cys-Cys signal for geranylgeranylation (Robinson et al, 1992;Wang et al, 1992).…”