The S-pombe orthologue of the S-cerevisiae mob1 gene is essential and functions in signalling the onset of septum formation

We have isolated the Schizosaccharomyces pombe orthologue of the Saccharomy ces cerevisiae MOB1 gene in a screen designed to enrich for septation mutan ts. The gene is essential, and cells lacking it display a phenotype typical of septation signalling network mutants. mob1p is located on both spindle pole bodies throughout mitosis, In addition it is also co-localised with th e medial ring later in mitosis, and hanks the septum as the medial ring con tracts. We also demonstrate that mob1p can be precipitated from cells in a complex with the septation regulating kinase sid2p.