Nin1p, a regulatory subunit of the 26S proteasome, is necessary for activation of Cdc28p kinase of Saccharomyces cerevisiae.

The nin1-1 mutant of Saccharomyces cerevisiae cannot perform the G1/S and G2/M transitions at restrictive temperatures. At such temperatures, nin1-1 strains fail to activate histone H1 kinase after release from alpha factor-imposed G1 block and after release from hydroxyurea-imposed S block. The nin1-1 mutation shows synthetic lethality with certain cdc28 ...
mutant alleles such as cdc28-IN. Two lines of evidence indicate that Nin1p is a component of the 26S proteasome complex: (i) Nin1p, as well as the known component of the 26S proteasome, shifted to the 26S proteasome peak in the glycerol density gradient after preincubation of crude extract with ATP-Mg2+, and (ii) nin1-1 cells accumulated polyubiquitinated proteins under restrictive conditions. These results suggest that activation of Cdc28p kinase requires proteolysis. We have cloned a human cDNA encoding a regulatory subunit of the 26S proteasome, p31, which was found to be a homolog of Nin1p.
Mesh Terms:
Amino Acid Sequence, Animals, Base Sequence, Biopolymers, CDC28 Protein Kinase, S cerevisiae, Cell Division, Enzyme Activation, Fungal Proteins, Gene Expression Regulation, Fungal, Genes, Fungal, Genes, Lethal, Humans, Molecular Sequence Data, Mutation, Peptide Hydrolases, Polyubiquitin, Proteasome Endopeptidase Complex, Proteins, Rats, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Homology, Amino Acid, Ubiquitins
EMBO J.
Date: Jul. 03, 1995
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