Over-expression of S. cerevisiae G1 cyclins restores the viability of alg1 N-glycosylation mutants.
In budding yeast, one of three G1 cyclins is required for progression though START, when cells commit to a further round of cell division. We have identified mutations in ALG1 (ERC14), a gene required for N-glycosylation, which are inviable in a cln1 cln2 background but are rescued by over-expression of CLNs. CLN1 and CLN2 are much more efficient than CLN3 in rescuing the erc14-1 allele. The erc14-1 allele results in a significant N-glycosylation defect, and no rescue of this defect by CLN1 over-expression was detected. These data suggest that CLN over-expression could be allowing cells to live with lower levels of N-glycosylation, possibly by overcoming a checkpoint sensitive to N-glycosylation capacity. A plasmid suppressor of alg1, PSA1, encodes a 361 amino-acid protein with homology to NDP-hexose pyrophosphorylases, the enzymes that catalyze the formation of activated sugar nucleotides. PSA1 is an essential gene, and PSA1 transcription is nearly co-ordinately regulated with CLN2 transcription, peaking near START. Co-ordinate regulation of glycosylation, sugar nucleotide metabolism, and cell-cycle progression through G1 may be a feature that ensures adequate cell-wall precursors are present before bud emergence.
Benton
B K
BK
Rockefeller University, New York, NY 10021, USA.
Plump
S D
SD
Roos
J
J
Lennarz
W J
WJ
Cross
F R
FR
D000483:Alleles; D000595:Amino Acid Sequence; D000953:Antigens, Protozoan; D000954:Antigens, Surface / Q000235:genetics; D001483:Base Sequence; D016213:Cyclins / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics; D015966:Gene Expression Regulation, Fungal; D006031:Glycosylation; D008364:Mannosyltransferases / Q000235:genetics* / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D015800:Protozoan Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D014170:Transformation, Genetic
D000953:Antigens, Protozoan; D000954:Antigens, Surface; D016213:Cyclins; D005656:Fungal Proteins; D008562:Membrane Glycoproteins; D015800:Protozoan Proteins; C074496:prespore-specific antigen, Dictyostelium discoideum; D008364:Mannosyltransferases; C035777:chitobiosyldiphosphodolichol beta-mannosyltransferase