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

Abstract

Presenilin plays critical roles in the genesis of Alzheimer's disease and in LIN-12͞Notch signaling during development. Here, we describe a screen for 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 requires 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.A key factor in the development of Alzheimer's disease is the deposition of plaques formed from A␤ peptides. These peptides are released when the single-pass transmembrane protein ␤-amyloid precursor protein (␤-APP) is cleaved at the ␤ site in the extracellular domain and at a ␥ site in the transmembrane domain. Studies of familial Alzheimer's disease led to the identification of the presenilin 1 and presenilin 2 genes (reviewed in ref. 1). Presenilin is required for ␥-secretase cleavage of ␤-APP (2, 3), and the two presenilins seem to be functionally interchangeable (4-6). Studies with putative aspartyl proteaseactive site inhibitors indicate that presenilin may itself be the long elusive ␥-secretase (7,8).Presenilin is being intensively pursued as a key therapeutic target for the amelioration or prevention of Alzheimer's disease. The identification of factors that influence presenilin activity, synthesis, and stability will be important for maximizing the efficacy of drugs that are targeted against ␥-secretase and perhaps for identifying new therapeutic targets. Genetic analysis of presenilin in Caenorhabditis elegans offers one approach to identifying such factors.In C. elegans, there are two presenilins, sel-12 and hop-1, that can be studied by virtue of their involvement in LIN-12͞Notch signal transduction (9, 10). LIN-12͞Notch proteins are transmembrane proteins that act as receptors for intercellular signals that specify cell fates. Ligand binding to LIN-12͞Notch receptors leads to proteolytic cleavage within the transmembrane domain, which releases the intracellular domain so that it may translocate to the nucleus and activate transcription of target genes (see 11, 12). The transmembrane-cleavage event is analogous to the ␥-secretase-processing event that generates A␤ from ␤-amyloid precursor protein, and presenilin is essential also for the proteolytic cleavage that releases the intracellular domain of LIN12͞Notch proteins (11,12). Indeed, in C. elegans, concomitant depletion of both sel-12 and hop-1 activity causes the phenotypes as...

Glyceraldehyde 3-phosphate dehydrogenase is a SET-binding protein and regulates cyclin B-cdk1 activity

“…We have previously reported that p21 Cip1 interacts with the SET protein, which was firstly identified as a CAN-fusion gene in an acute undifferentiated leukemia (von Lindern et al, 1992;Adachi et al, 1994). SET belongs to a family of proteins, which includes the yeast nucleosome assembly protein NAP-I (Kawase et al, 1996), MB20 (Shen et al, 2001), Cell Division Antigen-1 (Chai et al, 2001), nucleolar transforming growth factor-b1 target (Ozbun et al, 2001), supressor of presenilin-2 (Wen et al, 2000) and testis-specific protein Y-encoded (Vogel et al, 1998).…”

Two suppressors ofsel-12encode C2H2zinc-finger proteins that regulate presenilin transcription inCaenorhabditis elegans

“…Table S1 at http://dev.biologists.org/supplemental/). (Eimer et al, 2002b;Jarriault and Greenwald, 2002;Wen et al, 2000). Furthermore, 43% of all hop-1(lg1501)/dpy-5(e61) I; sel-12(ar171) spr-3(by108) animals with only one remaining copy of hop-1 and no functional sel-12 gene display an Egl phenotype (Table 3).…”

“…It is possible that SPR-3 and SPR-4 may also function by recruiting conserved co-repressor complexes to the hop-1 locus. Three other Spr genes, spr-1, spr-2 and spr-5, encode proteins similar to components of known co-repressors (Eimer et al, 2002b;Jarriault and Greenwald, 2002;Wen et al, 2000). SPR-2 is a member of the Nucleosome Assembly Protein (NAP) family and is most similar to the human oncogene SET .…”

Mutations in genes involved in nonsense mediated decay ameliorate the phenotype of sel-12 mutants with amber stop mutations in Caenorhabditis elegans

“…Six genes (spr-1-spr-5 and sel-10) have been identified that strongly suppress the sel-12 defects [9][10][11][12][13][14]. In the strongest suppressor mutations, the penetrance of sel-12 defects is reduced to less than 10% and in the spr-3 gene to almost 0% [13].…”

“…Although spr-2 was the first spr gene to be cloned, how it suppresses sel-12 on a molecular level remains unknown [10]. Unlike sel-10 mutations, mutations in spr-2 have no obvious effects on lin-12 signaling [10].…”