Suppressors of the egg-laying defective phenotype of <i>sel-12</i> presenilin mutants implicate the CoREST corepressor complex in LIN-12/Notch signaling in <i>C. elegans</i>

<jats:p>Presenilin is an essential component of the LIN-12/Notch signaling pathway and also plays a critical role in the genesis of Alzheimer's disease. Previously, a screen for suppressors of the egg-laying defective phenotype caused by partial loss of presenilin activity in<jats:italic>Caenorhabditis elegans</jats:italic> identified a number of new <jats:italic>spr</jats:italic>genes that are potentially involved in the regulation of LIN-12/Notch signaling or presenilin activity. Here we report the molecular identity of two <jats:italic>spr</jats:italic> genes, <jats:italic>spr-1</jats:italic> and <jats:italic>spr-5</jats:italic>. Our genetic analysis indicates that loss of <jats:italic>spr-1</jats:italic> elevates<jats:italic>lin-12/Notch</jats:italic> gene activity in many different cell fate decisions, suggesting that <jats:italic>spr-1</jats:italic> is a negative regulator of LIN-12/Notch signaling. Sequence analysis revealed that <jats:italic>spr-1</jats:italic>is an ortholog of human CoREST, a known corepressor. SPR-1 is localized to the nucleus and acts in a cell-autonomous manner; furthermore, human CoREST can substitute for SPR-1 in <jats:italic>C. elegans</jats:italic>. We also show that <jats:italic>spr-5</jats:italic> encodes a homolog of p110b, another known member of the CoREST corepressor complex. Our results suggest that the CoREST corepressor complex might be functionally conserved in worms, and we discuss the potential role of SPR-1 and SPR-5 in the repression of transcription of genes involved in, or downstream of, LIN-12/Notch signal transduction.</jats:p>