Functional analysis of syp1, a novel substrate of the serine/threonine kinase prk1

Abstract

In budding yeast, the actin and septin cytoskeletons are important for the establishment of cell polarity. During the cell cycle, these cytoskeletons undergo dramatic reorganization which is regulated by many cytoskeleton-associated proteins. In this study, Syp1p has been found to have functional interactions with the actin cytoskeleton. Syp1p is a new substrate of Prk1p, a kinase that regulates actin dynamics. Syp1p colocalizes with actin cytoskeleton whose integrity is required for the polarized localization of Syp1p. Syp1p can physically interact with the actin-associated protein Sla1p. Furthermore, Syp1p overexpression suppresses the defects of BNI1 deletion mutant. In addition to its roles in actin cytoskeleton, Syp1p is also discovered to be a new regulator of the septin dynamics. Syp1p colocalizes and physically interacts with septins. Syp1p overexpression disorganizes septin structure and induces the Swe1p-dependent elongated bud phenotype. Syp1p also regulates the organization of septins in different cell cycle stages.