Structure and function of the fourth subunit (Dpb4p) of DNA polymerase epsilon in Saccharomyces cerevisiae.
DNA polymerase epsilon (Polepsilon) of Saccharomyces cerevisiae is purified as a complex of four polypeptides with molecular masses of >250, 80, 34 (and 31) and 29 kDa as determined by SDS-PAGE. The genes POL2, DPB2 and DPB3, encoding the catalytic Pol2p, the second (Dpb2p) and the third largest subunits (Dpb3p) of the complex, respectively, were previously cloned and characterised. This paper reports the partial amino acid sequence of the fourth subunit (Dpb4p) of Polepsilon. This protein sequence matches parts of the predicted amino acid sequence from the YDR121w open reading frame on S.cerevisiae chromosome IV. Thus, YDR121w was renamed DPB4. A deletion mutant of DPB4 (Deltadpb4) is not lethal, but chromosomal DNA replication is slightly disturbed in this mutant. A double mutant haploid strain carrying the Deltadpb4 deletion and either pol2-11 or dpb11-1 is lethal at all temperatures tested. Furthermore, the restrictive temperature of double mutants carrying Deltadpb4 and dpb2-1, rad53-1 or rad53-21 is lower than in the corresponding single mutants. These results strongly suggest that Dpb4p plays an important role in maintaining the complex structure of Polepsilon in S.cerevisiae, even if it is not essential for cell growth. Structural homologues of DPB4 are present in other eukaryotic genomes, suggesting that the complex structure of S. cerevisiae Polepsilon is conserved in eukaryotes.
Ohya
T
T
Department of Biochemistry and Molecular Biology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
Maki
S
S
Kawasaki
Y
Y
Sugino
A
A
D020816:Amino Acid Motifs; D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics; D064447:Checkpoint Kinase 2; D017124:Conserved Sequence; D004257:DNA Polymerase II / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004258:DNA Polymerase III; D004261:DNA Replication / Q000235:genetics; D004259:DNA-Directed DNA Polymerase; D004795:Enzyme Stability; D004843:Epistasis, Genetic; D005434:Flow Cytometry; D005656:Fungal Proteins / Q000235:genetics; D017353:Gene Deletion; D020043:Genes, Essential / Q000235:genetics; D005800:Genes, Fungal / Q000235:genetics; D006657:Histones / Q000737:chemistry; D020035:Holoenzymes / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D011485:Protein Binding; D017510:Protein Folding; D011494:Protein Kinases / Q000235:genetics; D017346:Protein Serine-Threonine Kinases; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016196:S Phase; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins; D013696:Temperature
D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D006657:Histones; D020035:Holoenzymes; D021122:Protein Subunits; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; D017346:Protein Serine-Threonine Kinases; C067022:RAD53 protein, S cerevisiae; D004257:DNA Polymerase II; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase; C095943:POL31 protein, S cerevisiae