The many faces of shugoshin, the "guardian spirit," in chromosome segregation

Abstract

Since it was first identified in Drosophila as a centromeric protein, MEI-S332/Shugoshin (Sgo1) has been an enigma. It is neither a kinase nor a phosphatase, but Sgo1's many functions are often attributable to protein-protein interactions that require Sgo1's presence to localize and/or function properly in a timely manner. Though much has been reported about Sgo1's role in ensuring proper genome segregation through its regulatory role in maintaining cohesion through protection of centromeric cohesin, several additional functions have been identified that are less well characterized. In higher eukaryotes Sgo2 and a splice variant of Sgo1 make up a small family of shugoshin proteins, whereas in budding yeast a single Sgo1 exists, and available data suggest that the many functions carried out by Sgo2 and the splice variant are handled exclusively by the Sgo1 homolog in yeast. In fact, the function of the mammalian splice variant is the factor that has revealed a new possible role for shugoshin in centrosome regulation, which may be related mechanistically to its task in protection of centromeric cohesin. New evidence in budding yeast supports this line of reasoning, which may represent an exciting new advance in exposing the myriad faces of the guardian spirit. ©2009 Landes Bioscience.