spr-2, a suppressor of the egg-laying defect caused by loss of sel-12 presenilin in Caenorhabditis elegans, is a member of the SET protein subfamily

Presenilin plays critical roles in the genesis of Alzheimer's disease and in UN-12/Notch signaling during development. Here, we describe a screen far genes that influence presenilin level or activity in Caenorhabditis elegans. We identified four spr (suppressor of presenilin) genes by reverting the egg-laying defective phenotype caused by a null allele of the sel-12 presenilin gene. We analyzed the spr-2 gene in some detail. We show that loss of spr-2 activity suppresses the egg-laying defective phenotype of different sel-12 alleles and re quires activity of the hop-1 presenilin gene, suggesting that suppression is accomplished by elevating presenilin activity rather than by bypassing the need for presenilin activity. We also show that SPR-2 is a nuclear protein and is a member of a protein subfamily that includes human SET, which has been identified in numerous different biochemical assays and at translocation breakpoints associated with a subtype of acute myeloid leukemia.