A Bni4-Glc7 phosphatase complex that recruits chitin synthase to the site of bud emergence.
Bni4 is a scaffold protein in the yeast Saccharomyces cerevisiae that tethers chitin synthase III to the bud neck by interacting with septin neck filaments and with Chs4, a regulatory subunit of chitin synthase III. We show herein that Bni4 is also a limiting determinant for the targeting of the type 1 serine/threonine phosphatase (Glc7) to the bud neck. Yeast cells containing a Bni4 variant that fails to associate with Glc7 fail to tether Chs4 to the neck, due in part to the failure of Bni4(V831A/F833A) to localize properly. Conversely, the Glc7-129 mutant protein fails to bind Bni4 properly and glc7-129 mutants exhibit reduced levels of Bni4 at the bud neck. Bni4 is phosphorylated in a cell cycle-dependent manner and Bni4(V831A/F833A) is both hyperphosphorylated and mislocalized in vivo. Yeast cells lacking the protein kinase Hsl1 exhibit increased levels of Bni4-GFP at the bud neck. GFP-Chs4 does not accumulate at the incipient bud site in either a bni4::TRP1 or a bni4(V831A/F833A) mutant but does mobilize to the neck at cytokinesis. Together, these results indicate that the formation of the Bni4-Glc7 complex is required for localization to the site of bud emergence and for subsequent targeting of chitin synthase.
Kozubowski
Lukasz
L
Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71130, USA.
Panek
Heather
H
Rosenthal
Ashley
A
Bloecher
Andrew
A
DeMarini
Douglas J
DJ
Tatchell
Kelly
K
D002455:Cell Division / Q000502:physiology; D002687:Chitin Synthase / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
D029701:Saccharomyces cerevisiae Proteins; D002687:Chitin Synthase; D011494:Protein Kinases; C106494:HSL1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; C092048:GLC7 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1