Cdc4p, a contractile ring protein essential for cytokinesis in Schizosaccharomyces pombe, interacts with a phosphatidylinositol 4-kinase

The proposed function of Cdc4p, an essential contractile ring protein in Schizosaccharomyces pombe, is that of a myosin essential light chain. However, five conditionally lethal cdc4 alleles exhibit complementation in diploids. Such interallelic complementation is not readily explained if the sole f...

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Bibliographic Details
Published in:	The Journal of biological chemistry Vol. 276; no. 8; pp. 5932 - 5942
Main Authors:	Desautels, M, Den Haese, J P, Slupsky, C M, McIntosh, L P, Hemmingsen, S M
Format:	Journal Article
Language:	English
Published:	United States 23-02-2001
Subjects:	1-Phosphatidylinositol 4-Kinase - metabolism Amino Acid Sequence Binding Sites Carrier Proteins - metabolism Cdc4 protein Cell Cycle Proteins - genetics Cell Cycle Proteins - metabolism Cell Division - physiology Cytoskeletal Proteins F-Box Proteins Fungal Proteins - metabolism Gene Library Molecular Sequence Data Myosin Heavy Chains Myosin Type II Myosin Type V Myosins - metabolism phosphatidylinositol 4-kinase Point Mutation Protein Binding Saccharomyces cerevisiae Proteins Schizosaccharomyces - metabolism Schizosaccharomyces pombe Schizosaccharomyces pombe Proteins Sequence Alignment Two-Hybrid System Techniques Ubiquitin-Protein Ligases
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Summary:	The proposed function of Cdc4p, an essential contractile ring protein in Schizosaccharomyces pombe, is that of a myosin essential light chain. However, five conditionally lethal cdc4 alleles exhibit complementation in diploids. Such interallelic complementation is not readily explained if the sole function of Cdc4p is that of a myosin essential light chain. Complementation of cdc4 alleles could occur only if different mutant forms can assemble into an active oligomeric complex or if Cdc4p has more than one essential function. To search for other proteins that may interact with Cdc4p, we performed a two-hybrid screen and identified two such candidates: one similar to Saccharomyces cerevisiae Vps27p and the other a putative phosphatidylinositol (PI) 4-kinase. Binding of Cdc4p to the latter and to myosin heavy chain (Myo2p) was confirmed by immunosorbent assays. Deletion studies demonstrated interaction between the Cdc4p C-terminal domain and the PI 4-kinase C-terminal domain. Furthermore, interaction was abolished by the Cdc4p C-terminal domain point mutation, Gly107 to Ser. This allele also causes failure of cytokinesis. Ectopic expression of the PI 4-kinase C-terminal domain caused cytokinesis defects that were most extreme in cells carrying the G107S allele. We suggest that Cdc4p plays multiple roles in cytokinesis and that interaction with a PI 4-kinase may be important for contractile ring assembly and/or function.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0021-9258
DOI:	10.1074/jbc.M008715200