SPK-1, an SR protein kinase, inhibits programmed cell death in Caenorhabditis elegans.

To identify genes involved in protecting cells from programmed cell death in Caenorhabditis elegans, we performed a genetic screen to isolate mutations that cause an increase in the number of programmed cell deaths. We screened for suppressors of the cell-death defect caused by a partial loss-of-function mutation in ced-4, which encodes an Apaf-1 homolog that promotes programmed cell death by activating the caspase CED-3. We identified one extragenic ced-4 suppressor, which has a mutation in the gene spk-1. The spk-1 gene encodes a protein homologous to serine-arginine-rich (SR) protein kinases, which are thought to regulate splicing. Previous work suggests that ced-4 can be alternatively spliced and that the splice variants function oppositely, with the longer transcript (ced-4L) inhibiting programmed cell death. spk-1 might promote cell survival by increasing the amount of the protective ced-4L splice variant. We conclude that programmed cell death in C. elegans is regulated by an alternative splicing event controlled by the SR protein kinase SPK-1.