Correct regulation of the septation initiation network in Schizosaccharomyces pombe requires the activities of par1 and par2.
In Schizosaccharomyces pombe, the initiation of cytokinesis is regulated by a septation initiation network (SIN). We previously reported that deletion of par1 and par2, two S. pombe genes encoding B' regulatory subunits of protein phosphatase 2A, causes a multiseptation phenotype, very similar to that seen in hyperactive SIN mutants. In this study, we examined the genetic interactions between par deletions and mutations in the genes encoding components of SIN and found that deletion of par1 and par2 suppressed the morphological and viability defects caused by overproduction of Byr4p and rescued a loss-of-function allele of spg1. However, par deletions could not suppress any mutations in genes downstream of spg1 in the SIN pathway. We showed further that, in suppressing the lethality of a spg1 loss-of-function allele, the correct localization of Cdc7p to the spindle pole body (SPB), which is normally lost in spg1 mutant cells, was restored. The fact that par mutant cells themselves exhibited a symmetric localization of Cdc7p to SPBs indicated a hyperactivity of SIN in such cells. On the basis of our epistasis analyses and cytological studies, we concluded that par genes normally negatively regulate SIN at or upstream of cdc7, ensuring that multiple rounds of septation do not occur.
Jiang
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Department of Biology, Syracuse University, Syracuse, New York 13244, USA.
Hallberg
R L
RL
D000483:Alleles; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism / Q000502:physiology*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D016296:Mutagenesis; D009154:Mutation; D010641:Phenotype; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D054648:Protein Phosphatase 2; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012568:Schizosaccharomyces / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins; D013696:Temperature
D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D008164:Luminescent Proteins; C410165:PAR1 protein, S pombe; C410166:PAR2 protein, S pombe; D011993:Recombinant Fusion Proteins; D029702:Schizosaccharomyces pombe Proteins; D049452:Green Fluorescent Proteins; C489406:cdc7 protein, S pombe; D017346:Protein Serine-Threonine Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2