THE ROLE OF SACCHAROMYCES-CEREVISIAE CORONIN IN THE ACTIN AND MICROTUBULE CYTOSKELETONS

Coronin was originally identified as a cortical protein associated wit h the actin cytoskeleton in Dictyostelium [1]. More recent studies hav e revealed that coronin is involved in actin-based motility, cytokines is and phagocytosis [2,3]. Here, we describe the identification of a s ingle homolog of coronin in Saccharomyces cerevisiae, which we show lo calizes to cortical actin patches in an actin-dependent manner. Unlike Dictyostelium mutants that lack coronin, yeast strains lacking coroni n had no detectable defects in actin-based processes. This may reflect differences in the functions of the actin cytoskeleton in these two o rganisms. Previous studies have shown that cortical actin may mediate astral microtubule-based movements of the mitotic spindle in S. cerevi siae [4,5] and that, during mitosis in Dictyostelium, the regions of t he cell cortex that overlap with astral microtubules become enriched i n actin and coronin [6]. We therefore examined whether yeast lacking c oronin had defects in the microtubule cytoskeleton. The mutant strains had increased sensitivity to the microtubule destabilizing drug benom yl and an increased number of large-budded cells with short spindles. Further examination of microtubule-related processes, including spindl e formation, migration of the mitotic spindle to the bud neck, spindle elongation, and translocation of the elongating spindle through the b ud neck, failed to reveal any defects in the coronin mutant. Taken tog ether, these results suggest that S. cerevisiae coronin is a component of the actin cytoskeleton that may interact with the microtubule cyto skeleton. (C) Current Biology Ltd ISSN 0960-9822.