Myo51 in mating and meiosis

Class V myosins are actin-associated motor proteins involved in cellular transport. Of the two class V myosins found in fission yeast, Myo52 has several known functions, but the cellular roles of Myo51 were previously unknown. On page 4330, Daniel Mulvihill and colleagues now characterise the role of Myo51 in the sexual life cycle of Schizosaccharomyces pombe and show that this protein has different functions during mating and meiosis. First, they show that Myo51 recruits to the site of cell fusion; this requires the actin cytoskeleton and the formin Fus1, which polymerises actin filaments at the projection tips of mating cells. Localised Myo51 then disperses during nuclear fusion, before localising to the periphery of the spindle pole body (SPB) in an actin-independent manner throughout meiotic chromosome segregation. Deletion of the myo51 gene causes abnormal meiotic chromosome segregation and spore formation, confirming a role for Myo51 in maintaining SPB integrity during meiosis. Whether Myo51 is involved in delivering cargos to the SPB, or whether it acts as a tether or tension sensor at this site, requires further study.