The Saccharomyces cerevisiae SOC8-1 gene and its relationship to a nucleotide kinase.
The yeast SOC8-1 gene was originally identified by partial complementation of cdc8 mutant strains. We have carried out Bal31 deletion analysis of the SOC8-1 gene to define the minimal size which is required for the complementation of the cdc8 mutation. When the SOC8-1 gene is cloned in a multicopy plasmid, it enables temperature-resistant growth in the cdc8 mutant strain, while the SOC8-1 gene in a single copy plasmid does not. Thus, its suppression of the cdc8 mutant is dosage dependent. The high copy number vector carrying the SOC8-1 gene can complement five different cdc8 alleles, indicating that the suppression is not allele specific. Since CDC8 encodes thymidylate kinase, cells bearing a high copy number plasmid containing SOC8-1 gene were tested for the ability to phosphorylate several nucleoside monophosphates, including UMP, GMP and dTMP. Significantly increased phosphorylation activity was observed, suggesting that SOC8-1 encodes a nucleotide kinase. Both restriction enzyme analysis of the SOC8-1 gene and partial purification of the overproduced kinase in SOC8-1 overproducing strains suggest that SOC8-1 may be allelic with URA6. Consistent with these results, both SOC8-1 and URA6 are located on chromosome XI. Thus, one possible suppression mechanism is that SOC8-1 may provide a trans-acting dTMP kinase activity, bypassing the cdc8 gene defect.
Choi
W J
WJ
Department of Pediatrics and Microbiology, University of Southern California School of Medicine, Los Angeles 90033.
Campbell
J L
JL
Kuo
C L
CL
Jong
A Y
AY
D002455:Cell Division; D002874:Chromosome Mapping; D005796:Genes; D005800:Genes, Fungal; D005838:Genotype; D009154:Mutation; D009703:Nucleoside-Phosphate Kinase / Q000235:genetics; D010957:Plasmids; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology / Q000235:genetics*
D009703:Nucleoside-Phosphate Kinase; C020093:dTMP kinase