Truncated Sla1 induces haploid meiosis through the Pat1-Mei2 system in fission yeast.

We previously reported that expression of Sla1DeltaC, a truncated form of Sla1, induces ectopic meiosis in heterothallic fission yeast and this was possibly due to the inhibition of Pat1 kinase by Sla1DeltaC. Here we found mei2 mRNA and the Mei2 protein accumulated and stability of the Mei2 protein increased when Sla1DeltaC was expressed. The former two results are considered to be the consequence of de-repression of Ste11, which is the transcription factor of mei2 and negatively regulated by Pat1 kinase. The latter result reflects the consequence of deregulation of Mei2 by Pat1 kinase. In addition, Ste11 accumulated in the nucleus when Sla1DeltaC was expressed. All these data consistently support the idea that the action of Sla1DeltaC is to inactivate Pat1 kinase.