Plays a major role in controlling sexual phenotype (PubMed:1339311). Terminal global regulator in a well-characterized cascade of sex-determining genes (PubMed:8367286). Promotes female development (PubMed:11124807). Interacts with tra-2 to promote spermatogenesis (PubMed:11250902). Promotes spermatogenesis through the Tip60 HAT complex and by regulating the expression of genes, such as fog-3, required for male development (By similarity). Association with chromatin and at the fog-3 promoter requires wdr-5.1, and may also require wdr-5.2 (PubMed:24682813). With trr-1, activates the fog-3 gene to determine sperm/oocyte cell fate (By similarity). In hermaphrodites, binds to an intronic regulatory site in the ceh-30 gene, preventing ceh-30 transcription and thereby preventing survival of the CEM (cephalic male) sensory neurons (PubMed:18056428). Represses the expression of the transcription factor dmd-3 in hermaphrodites to govern the timing and extent of male tail tip morphogenesis (PubMed:18550714). Plays a role in controlling the sex-specific differentiation of PHC sensory neurons and represses the development of male-specific morphological features (PubMed:28065609). Interacts with the MX regulatory domain of tra-2. Localization with chromatin in the nucleus in part depends on normal function of wdr-5.1. Expressed in intestine and gonads (at protein level). Isoform b is expressed abundantly in second larval (L2) stage. Isoform a is more abundant in embryos. Only isoform a (Tra-1L), is thought to bind DNA. Zinc fingers 3, 4 and 5 are the most important for DNA binding; removal of finger 5 almost abolishes DNA binding and prevents the selection of binding sites. Belongs to the GLI C2H2-type zinc-finger protein family.