S. pombe gene sds22+ essential for a midmitotic transition encodes a leucine-rich repeat protein that positively modulates protein phosphatase-1.
The fission yeast dis2+ gene encodes one of the two type 1 protein phosphatases (PP1) in this organism. Its semidominant mutant dis2-11 is defective in mitosis. Here we report the characterization of a high dosage suppressor, sds22+, that complements dis2-11. Sequencing of the cloned sds22+ gene predicts a novel 30 kd protein, which consists almost entirely of leucine-rich 22 amino acid repeats and is enriched in the insoluble nuclear fraction. sds22+ is an essential gene required for the mitotic metaphase/anaphase transition; gene disruption causes cell cycle arrest at midmitosis. Unexpectedly, the sds22+ gene becomes dispensable upon high dosage of the PP1 genes. The sds22+ product appears to facilitate PP1-dependent dephosphorylation, but does not substitute PP1. We propose that the sds22+ protein forms a repeating helical rod that is capable of enhancing a PP1-dependent dephosphorylation activity that is essential in midmitosis.
Ohkura
H
H
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
Yanagida
M
M
D000595:Amino Acid Sequence; D001483:Base Sequence; D018797:Cell Cycle Proteins; D005656:Fungal Proteins / Q000235:genetics*; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D007930:Leucine; D008938:Mitosis; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010749:Phosphoprotein Phosphatases / Q000235:genetics*; D011487:Protein Conformation; D054645:Protein Phosphatase 1; D015183:Restriction Mapping; D012568:Schizosaccharomyces / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D029702:Schizosaccharomyces pombe Proteins; D012689:Sequence Homology, Nucleic Acid
D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D009687:Nuclear Proteins; D029702:Schizosaccharomyces pombe Proteins; C066843:sds22 protein, S pombe; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D007930:Leucine