Two suppressors of sel-12 encode C sub(2)H sub(2) zinc-finger proteins that regulate presenilin transcription in Caenorhabditis elegans

Mutations in presenilin genes are associated with familial Alzheimer's disease in humans and affect LIN-12/Notch signaling in all organisms tested so far. Loss of sel-12 presenilin activity in Caenorhabditis elegans results in a completely penetrant egg-laying defect. In screens for extragenic suppressors of the sel-12 egg-laying defect, we have isolated mutations in at least five genes. We report the cloning and characterization of spr-3 and spr-4, which encode large basic C sub(2)H sub(2) zinc-finger proteins. Suppression of sel-12 by spr-3 and spr-4 requires the activity of the second presenilin gene, hop-1. Mutations in both spr-3 and spr-4 de-repress hop-1 transcription in the early larval stages when hop-1 expression is normally nearly undetectable. As sel-12 and hop-1 are functionally redundant, this suggests that mutations in spr-3 and spr-4 bypass the need for one presenilin by stage-specifically de-repressing the transcription of the other. Both spr-3 and spr-4 code for proteins similar to the human REST/NRSF (Re1 silencing transcription factor/neural-restrictive silencing factor) transcriptional repressors. As other Spr genes encode proteins homologous to components of the CoREST co-repressor complex that interacts with REST, and the INHAT (inhibitor of acetyltransferase) co-repressor complex, our data suggest that all Spr genes may function through the same mechanism that involves transcriptional repression of the hop-1 locus.