The Schizosaccharomyces pombe sep15+ gene encodes a protein homologous to the Med8 subunit of the Saccharomyces cerevisiae transcriptional mediator complex.

We previously described the isolation of mutants defective in cell separation and the identification of 16 sep genes with complex functions. Here we report on the cloning and analysis of sep15+. The deduced amino acid sequence of the Sep15 protein shows significant homology to Med8, a component of the Saccharomyces cerevisiae transcription mediator complex. The mutation sep15-598 confers hyphal morphology and causes temperature-sensitive lethality. Disruption of sep15+ is lethal, indicating that Sep15 exerts an essential function and its role in cell separation is indirect.