Component of the SDC complex that functions in sex determination and in X chromosome dosage compensation specifically in hermaphrodite (XX) animals (PubMed:2759421, PubMed:10364546). Required for the recruitment of the condensin I-like dosage compensation complex to the male sex-determining autosomal gene her-1, thereby contributing to its repression and initiating hermaphrodite sexual development (PubMed:2759421, PubMed:10364546, PubMed:14660541, PubMed:11937488). Plays a central role in X-chromosome recognition and in the recruitment and assembly of the dosage compensation complex and the dosage compensation protein dpy-21 onto the X chromosomes in hermaphrodites, which leads to a reduction of X-linked gene transcription and an equalization of X-linked gene expression between the sexes (PubMed:8939869, PubMed:8939870, PubMed:9458050, PubMed:9056777, PubMed:10364546, PubMed:14660541). May confer protection against toxicity induced by heavy metals such as arsenite (PubMed:25204677). Component of the SDC complex, which consists of sdc-1, sdc-2 and sdc-3. Within the complex, interacts with sdc-1 and sdc-3. Localizes specifically to X chromosomes in hermaphrodite (XX) embryos. Expressed in hermaphrodites (XX), but absent in males (XO) (at protein level). Expressed in embryos after the 40-cell stage and in adults. Results in high lethality of hermaphrodites (XX) and in masculinization of surviving XX animals (PubMed:2759421). Disrupts the X-chromosome specific localization of sdc-3, dpy-21, dpy-26, dpy-27 and mix-1 (PubMed:9056777, PubMed:8939869, PubMed:8939870, PubMed:9458050, PubMed:14660541). RNAi-mediated knockdown results in 86% viability of hermaphrodites (PubMed:23666922). RNAi-mediated knockdown results in increased sensitivity to the heavy metal arsenite (PubMed:25204677). RNAi-mediated knockdown reduces the viability of hermaphrodites to 19% in a double xol-1(y9) and sex-1(y263) mutant background (PubMed:23666922). RNAi-mediated knockdown reduces the viability of hermaphrodites to 11% in a triple sea-1(y356), xol-1(y9) and sex-1(y263) mutant background (PubMed:23666922). RNAi-mediated knockdown reduces the viability of hermaphrodites to 42% in a triple sea-2(y407), xol-1(y9) sex-1(y263) mutant background (PubMed:23666922). RNAi-mediated knockdown reduces the viability of hermaphrodites to 51% in a quadruple sea-1(y356), sea-2(y407), xol-1(y9) sex-1(y263) mutant background (PubMed:23666922).