PMID:8207058
| Citation |
Balasubramanian, MK, Hirani, BR, Burke, JD and Gould, KL (1994) The Schizosaccharomyces pombe cdc3+ gene encodes a profilin essential for cytokinesis. J. Cell Biol. 125:1289-301 |
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| Abstract |
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. |
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| Keywords |
Actins/isolation & purification; Amino Acid Sequence; Base Sequence; Cell Cycle Proteins; Cell Division/genetics; Cell Nucleus/ultrastructure; Cloning, Molecular; Contractile Proteins; Fluorescent Antibody Technique; Fungal Proteins/biosynthesis; Fungal Proteins/genetics; Fungal Proteins/isolation & purification; Genes, Fungal/genetics; Microfilament Proteins/biosynthesis; Microfilament Proteins/genetics; Microfilament Proteins/isolation & purification; Molecular Sequence Data; Mutation; Profilins; Recombinant Proteins/biosynthesis; Schizosaccharomyces/genetics; Schizosaccharomyces pombe Proteins; Sequence Analysis, DNA; Sequence Homology, Amino Acid |
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