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Genes Cells. 2002 Apr;7(4):375-84.

Tropomyosin is required for the cell fusion process during conjugation in fission yeast.

Author information

1
Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113-0033, Japan.

Abstract

BACKGROUND:

Tropomyosin is an actin-binding protein, which is thought to stabilize actin filaments and influence many aspects of F-actin. In fission yeast, the cdc8 gene encodes tropomyosin, and the gene product Cdc8p is known to be essential for the formation of the F-actin contractile ring and hence for cytokinesis in the mitotic cell cycle.

RESULTS:

We isolated fission yeast mutants that were defective in cell fusion during conjugation. One of them turned out to carry a point mutation in cdc8. We found that the original temperature-sensitive cdc8 mutant frequently failed to undergo cell fusion when mated at a semi-permissive temperature. Additional cdc8 mutants isolated by targeted mutagenesis also showed defects in both cell fusion and cytokinesis. A decrease in the amount of intracellular Cdc8p also affected both, but cell growth was more severely blocked than cell fusion in this case. Immunostaining revealed that Cdc8p was localized as a spot at the cell-to-cell attachment site during conjugation, without overlapping with F-actin patches.

CONCLUSIONS:

Tropomyosin Cdc8p is indispensable for cell fusion during conjugation in fission yeast. However, cell fusion appears to require fewer tropomyosin molecules than cytokinesis. We speculate that tropomyosin may organize a small F-actin-containing organelle at the cell-to-cell contact site in each mating cell, which plays a key role in cell fusion.

PMID:
11952834
[Indexed for MEDLINE]
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