The Saccharomyces cerevisiae actin cytoskeletal component Bsp1p has an auxiliary role in actomyosin ring function and in the maintenance of bud-neck structure.
Iqg1p is a component of the actomyosin contractile ring that is required for actin recruitment and septum deposition. Cells lacking Iqg1p function have an altered bud-neck structure and fail to form a functional actomyosin contractile ring resulting in a block to cytokinesis and septation. Here it is demonstrated that increased expression of the actin cytoskeleton associated protein Bsp1p bypasses the requirement for contractile ring function. This also correlates with reduced bud-neck width and remedial septum formation. Increased expression of this protein in a temperature-sensitive iqg1-1 background causes remedial septum formation at the bud neck that is reliant upon chitin synthase III activity and restores cell separation. The observed suppression correlates with a restoration of normal bud-neck structure. While Bsp1p is a component of the contractile ring, its recruitment to the bud neck is not required for the observed suppression. Loss of Bsp1p causes a brief delay in the redistribution of the actin cytoskeleton normally observed at the end of actin ring contraction. Compromise of Iqg1p function, in the absence of Bsp1p function, leads to a profound change in the distribution of actin and the pattern of cell growth accompanied by a failure to complete cytokinesis and cell separation.
Wright
Daniel J
DJ
Biomedical Sciences Unit, Biological Sciences, Lancaster University, Lancaster LA1 4YQ, United Kingdom.
Munro
Ewen
E
Corbett
Mark
M
Bentley
Adam J
AJ
Fullwood
Nigel J
NJ
Murray
Stephen
S
Price
Clive
C
D000199:Actins / Q000378:metabolism*; D000205:Actomyosin / Q000378:metabolism*; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D002686:Chitin / Q000096:biosynthesis; D002687:Chitin Synthase / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D005656:Fungal Proteins / Q000378:metabolism; D020935:MAP Kinase Signaling System; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D011485:Protein Binding; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013489:Suppression, Genetic; D013696:Temperature; D020703:ras GTPase-Activating Proteins / Q000378:metabolism
D000199:Actins; D033942:Adaptor Proteins, Vesicular Transport; C473114:Bsp1 protein, S cerevisiae; D005656:Fungal Proteins; C101203:IQ motif containing GTPase activating protein 1; D029701:Saccharomyces cerevisiae Proteins; D020703:ras GTPase-Activating Proteins; D002686:Chitin; D000205:Actomyosin; D002687:Chitin Synthase