Transcriptional regulator that plays a central role in lin-12/Notch and glp-1/Notch signaling pathways, involved in cell-cell communication that regulate a broad spectrum of cell-fate determinations (PubMed:8625826). Binds directly to the 5'-[A/G]TGGGAA-3' DNA consensus sequence, which is present in the regulatory region of several genes (PubMed:8625826, PubMed:18706403, PubMed:23615264, PubMed:15297877, PubMed:32196486, PubMed:21737278). Acts as a transcriptional repressor when it is not associated with Notch proteins (By similarity). When in a complex with a Notch intracellular domain (NICD) product of lin-12/Notch or glp-1/Notch, and transcription regulator lag-3, it may act as a transcriptional activator that activates transcription of target genes(PubMed:18381292, PubMed:10830967, PubMed:32196486, PubMed:9003776). Probably represses or activates transcription via the recruitment of chromatin remodeling complexes containing histone deacetylase or histone acetylase proteins, respectively (By similarity). Autonomously required in the germline for the stem cell fate, acting in the glp-1-dependent transcriptional activation of genes, including lst-1 and sygl-1 (PubMed:32196486). Involved in cell-fate specification during reproductive system development, by positively autoregulating its own expression, in response to lin-12/Notch signaling (PubMed:23615264, PubMed:32839181). Plays a role in Notch-dependent induction of left-right asymmetry in interneurons and motoneurons (PubMed:21737278). May repress expression of hlh-6, in a lin-12/Notch-independent manner (PubMed:18706403). Component of a complex consisting of at least a lin-12/Notch intracellular domain (NICD), lag-1, and lag-3 (PubMed:16530045, PubMed:10830967, PubMed:18381292). An NICD product of lin-12/Notch, including the RBP-j associated molecule (RAM) and ankyrin repeat (ANK) domains, interacts directly with lag-1 (PubMed:16530045, PubMed:10830967, PubMed:18381292, PubMed:9003776). In young adults, expressed in germ cells in the distal most ~10 cell diameters of the progenitor zone (PZ), and also in late pachytene, diplotene and diakinesis of oogenesis. Expressed in the precursor anchor cell and ventral uterine precursor cell (Z1.ppp, Z1.ppa, Z4.aaa, and Z4.aap) before cell specification, at early larval stage L2 (PubMed:23615264). Expressed in the ventral uterine cell (VU), but not in the anchor cell (AC), after specification, at late larval stage L2 (PubMed:23615264). Expressed in a dynamic pattern in the vulval precursor cells (VPCs) during vulval induction in larval stage L3 (PubMed:32839181). Expressed in somatic gonad cells, the distal tip cell (DTC), and all sheath and spermathecal cells, as well as in polyploid intestinal cells, in both the larval L4 and adult stages. RNAi-mediated knockdown ectopically up-regulates expression of hlh-6 outside pharyngeal gland cells. Belongs to the Su(H) family.