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 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.
Desautels
M
M
Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E5, Canada.
Den Haese
J P
JP
Slupsky
C M
CM
McIntosh
L P
LP
Hemmingsen
S M
SM
D019870:1-Phosphatidylinositol 4-Kinase / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology*; D003598:Cytoskeletal Proteins; D044783:F-Box Proteins; D005656:Fungal Proteins / Q000378:metabolism; D015723:Gene Library; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains; D024462:Myosin Type II; D024701:Myosin Type V; D009218:Myosins / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins; D016415:Sequence Alignment; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D044783:F-Box Proteins; D005656:Fungal Proteins; C077512:MYO2 protein, S cerevisiae; C434211:MYO2 protein, S pombe; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C513274:cdc4 protein, S pombe; D044767:Ubiquitin-Protein Ligases; D019870:1-Phosphatidylinositol 4-Kinase; C441760:PIK1 protein, S cerevisiae; D024462:Myosin Type II; D024701:Myosin Type V; D018995:Myosin Heavy Chains; D009218:Myosins