Yeast counterparts of subunits S5a and p58 (S3) of the human 26S proteasome are encoded by two multicopy suppressors of nin1-1.
Nin1p, a component of the 26S proteasome of Saccharomyces cerevisiae, is required for activation of Cdc28p kinase at the G1-S-phase and G2-M boundaries. By exploiting the temperature-sensitive phenotype of the nin1-1 mutant, we have screened for genes encoding proteins with related functions to Nin1p and have cloned and characterized two new multicopy suppressors, SUN1 and SUN2, of the nin1-1 mutation. SUN1 can suppress a null nin1 mutation, whereas SUN2, an essential gene, does not. Sun1p is a 268-amino acid protein which shows strong similarity to MBP1 of Arabidopsis thaliana, a homologue of the S5a subunit of the human 26S proteasome. Sun1p binds ubiquitin-lysozyme conjugates as do S5a and MBP1. Sun2p (523 amino acids) was found to be homologous to the p58 subunit of the human 26S proteasome. cDNA encoding the p58 component was cloned. Furthermore, expression of a derivative of p58 from which the N-terminal 150 amino acids had been removed restored the function of a null allele of SUN2. During glycerol density gradient centrifugation, both Sun1p and Sun2p comigrated with the known proteasome components. These results, as well as other structural and functional studies, indicate that both Sun1p and Sun2p are components of the regulatory module of the yeast 26S proteasome.
Kominami
K
K
Department of Biological Sciences, Graduate School of Science, University of Tokyo, Japan.
Okura
N
N
Kawamura
M
M
DeMartino
G N
GN
Slaughter
C A
CA
Shimbara
N
N
Chung
C H
CH
Fujimuro
M
M
Yokosawa
H
H
Shimizu
Y
Y
Tanahashi
N
N
Tanaka
K
K
Toh-e
A
A
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002498:Centrifugation / Q000379:methods; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D016153:Genes, Suppressor; D005990:Glycerol / Q000737:chemistry; D006801:Humans; D008969:Molecular Sequence Data; D009113:Muramidase / Q000378:metabolism; D009154:Mutation; D016366:Open Reading Frames; D010447:Peptide Hydrolases / Q000235:genetics* / Q000378:metabolism; D010957:Plasmids; D046988:Proteasome Endopeptidase Complex; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics; D014452:Ubiquitins / Q000378:metabolism
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; C083209:MBP1 protein, S cerevisiae; C498506:PSMD4 protein, human; D016601:RNA-Binding Proteins; C122019:RPN10 protein, S cerevisiae; C074096:RPN12 protein, S cerevisiae; C403291:RPN3 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D014452:Ubiquitins; D009113:Muramidase; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D005990:Glycerol