Molecular Genetic Analysis of Rts1p, a B′ Regulatory Subunit of Saccharomyces cerevisiae Protein Phosphatase 2A

Abstract

The Saccharomyces cerevisiae gene RTS1 encodes a protein homologous to a variable B-type regulatory subunit of the mammalian heterotrimeric serine/threonine protein phosphatase 2A (PP2A). We present evidence showing that Rts1p assembles into similar heterotrimeric complexes in yeast. Strains in which RTS1 has been disrupted are temperature sensitive (ts) for growth, are hypersensitive to ethanol, are unable to grow with glycerol as their only carbon source, and accumulate at nonpermissive temperatures predominantly as large-budded cells with a 2N DNA content and a nondivided nucleus. This cell cycle arrest can be overcome and partial suppression of the ts phenotype of rts1-null cells occurs if the gene CLB2, encoding a Cdc28 kinaseassociated B-type cyclin, is expressed on a high-copy-number plasmid. However, CLB2 overexpression has no suppressive effects on other aspects of the rts1-null phenotype. Expression of truncated forms of Rts1p can also partially suppress the ts phenotype and can fully suppress the inability of cells to grow on glycerol and the hypersensitivity of cells to ethanol. By contrast, the truncated forms do not suppress the accumulation of large-budded cells at high temperatures. Coexpression of truncated Rts1p and high levels of Clb2p fully suppresses the ts phenotype, indicating that the inhibition of growth of rts1-null cells at high temperatures is due to both stress-related and cell cycle-related defects. Genetic analyses show that the role played by Rts1p in PP2A regulation is distinctly different from that played by the other known variable B regulatory subunit, Cdc55p, a protein recently implicated in checkpoint control regulation.

Expression deconvolution: A reinterpretation of DNA microarray data reveals dynamic changes in cell populations

“…Deconvolution reveals that cln3⌬ cells show roughly equal proportions of G 1 and S phase cells, but no other phases. For each of the other strains, the observed deconvolution results match the defects observed by other techniques (17)(18)(19)(20)(21), such as the known post-S phase delay of cells overexpressing calmodulin [CMD1 (Tet)], which are defective in nuclear division (22), exhibiting a higher proportion of M and M͞G 1 cells in our analysis.…”

Modulation of TORC2 Signaling by a Conserved Lkb1 Signaling Axis in Budding Yeast

“…Previous studies suggested that Rts1 is a phospho-protein (Shu et al 1997), which suggested that feedback signals could be relayed via phosphorylation of Rts1. To investigate further, we raised an antibody that recognizes Rts1.…”

The Scaffolding A/Tpd3 Subunit and High Phosphatase Activity Are Dispensable for Cdc55 Function in the Saccharomyces cerevisiae Spindle Checkpoint and in Cytokinesis

“…TPD3 encodes the only A subunit, and two distinct B subunits, encoded by CDC55 and RTS1, are highly homologous to mammalian B and BЈ, respectively (7)(8)(9). Mutations of CDC55 are viable, but yield defects in cytokinesis and in the spindle checkpoint and result in abnormal cell morphology.…”