The Schizosaccharomyces pombe cdc3+ gene encodes a profilin essential for cytokinesis.

Balasubramanian MK, Hirani BR, Burke JD, Gould KL
J Cell Biol. 1994 125 (6): 1289-301

PMID: 8207058 · PMCID: PMC2290924 · DOI:10.1083/jcb.125.6.1289

The fission yeast Schizosaccharomyces pombe divides by medial fission and, like many higher eukaryotic cells, requires the function of an F-actin contractile ring for cytokinesis. In S. pombe, a class of cdc- mutants defective for cytokinesis, but not for DNA replication, mitosis, or septum synthesis, have been identified. In this paper, we present the characterization of one of these mutants, cdc3-124. Temperature shift experiments reveal that mutants in cdc3 are incapable of forming an F-actin contractile ring. We have molecularly cloned cdc3 and used the cdc3+ genomic DNA to create a strain carrying a cdc3 null mutation by homologous recombination in vivo. Cells bearing a cdc3-null allele are inviable. They arrest the cell cycle at cytokinesis without forming a contractile ring. DNA sequence analysis of the cdc3+ gene reveals that it encodes profilin, an actin-monomer-binding protein. In light of recent studies with profilins, we propose that Cdc3-profilin plays an essential role in cytokinesis by catalyzing the formation of the F-actin contractile ring. Consistent with this proposal are our observations that Cdc3-profilin localizes to the medial region of the cell where the F-actin contractile ring forms, and that it is essential for F-actin ring formation. Cells overproducing Cdc3-profilin become elongated, dumbbell shaped, and arrest at cytokinesis without any detectable F-actin staining. This effect of Cdc3-profilin overproduction is relieved by introduction of a multicopy plasmid carrying the actin encoding gene, act1+. We attribute these effects to potential sequestration of actin monomers by profilin, when present in excess.

MeSH Terms (20)

Actins Amino Acid Sequence Base Sequence Cell Cycle Proteins Cell Division Cell Nucleus Cloning, Molecular Contractile Proteins Fluorescent Antibody Technique Fungal Proteins Genes, Fungal Microfilament Proteins Molecular Sequence Data Mutation Profilins Recombinant Proteins Schizosaccharomyces Schizosaccharomyces pombe Proteins Sequence Analysis, DNA Sequence Homology, Amino Acid

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