Abstract
Cytokinesis and cell separation are critical events in the cell cycle. We show that Endosomal Sorting Complex Required for Transport (ESCRT) genes are required for cell separation in Schizosaccharomyces pombe. We identify genetic interactions between ESCRT proteins and polo and aurora kinases and Cdc14 phosphatase that manifest as impaired growth and exacerbated defects in septation, suggesting that the encoded proteins function together to control these processes. Furthermore, we observed defective endosomal sorting in mutants of plo1, ark1 and clp1, as has been reported for ESCRT mutants, consistent with a role for these kinases in the control of ESCRT function in membrane traffic. Multiple observations indicate functional interplay between polo and ESCRT components: firstly, two-hybrid in vivo interactions are reported between Plo1p and Sst4p, Vps28p, Vps25p, Vps20p and Vps32p; secondly, co-immunoprecipitation of human homologues of Vps20p, Vps32p, Vps24p and Vps2p by human Plk1; and thirdly, in vitro phosphorylation of budding yeast Vps32p and Vps20p by polo kinase. Two-hybrid analyses also identified interactions between Ark1p and Vps20p and Vps32p, and Clp1p and Vps28p. These experiments indicate a network of interactions between ESCRT proteins, plo1, ark1 and clp1 that coordinate membrane trafficking and cell separation in fission yeast.
Highlights
Endosomal Sorting Complex Required for Transport (ESCRT) proteins mediate membrane scission events involved in the down-regulation of ubiquitin-labelled receptors via the multivesicular body (MVB) pathway and in HIV budding from host cells [1]
ESCRT mutants in fission yeast display cell division defects There is increasing evidence that ESCRT proteins play a role during cytokinesis and abscission in eukaryotic cells [2,8,19]
To test whether ESCRT proteins are involved in cell separation in fission yeast, we examined the effect of chromosomal deletions of individual genes encoding the various classes of ESCRT proteins on cytokinesis and septation
Summary
ESCRT proteins mediate membrane scission events involved in the down-regulation of ubiquitin-labelled receptors via the multivesicular body (MVB) pathway and in HIV budding from host cells [1]. During MVB formation, ESCRT proteins are recruited sequentially to the endosomal membrane: ESCRT-0 sequesters ubiquitinated cargo destined for degradation, ESCRT-I and II deform the peripheral membrane to produce a bud and ESCRT-III constricts the bud neck to form an intralumenal vesicle [3]. Thereafter, the AAAATPase Vps4p redistributes ESCRT-III subunits into the cytoplasm to mediate further MVB formation; it is thought that the association of ESCRT-III and Vps4p forms the conserved membrane scission machinery in all ESCRT functions [4].
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