Required for both chromosome condensation and segregation during mitosis and meiosis and X-chromosome dosage compensation depending on its binding partners (PubMed:19119011, PubMed:19781752, PubMed:3779843, PubMed:18198337). Regulatory subunit of the condensin I complex, a complex required for conversion of interphase chromatin into mitotic-like condense chromosomes (PubMed:19781752, PubMed:19119011). The condensin I complex probably introduces positive supercoils into relaxed DNA in the presence of type I topoisomerases and converts nicked DNA into positive knotted forms in the presence of type II topoisomerases (By similarity). The condensin I complex function is required for proper chromosome segregation in mitosis and meiosis (PubMed:19119011). As a member of the condensin I complex, further controls the crossover number and distribution in meiosis by restricting double strand break formation, possibly by influencing higher-order chromosome structure (PubMed:18198337, PubMed:19781752). Plays a role in robust cytokinesis upon presence of chromatin obstructions (PubMed:23684975). Also a member of the condensin I-like dosage compensation complex that associates specifically with hermaphrodite X chromosomes to reduce their gene transcription during interphase, possibly through chromatin reorganization (PubMed:3779843, PubMed:19119011, PubMed:15557118). Component of the condensin I complex, which contains the mix-1/SMC2 and smc-4/SMC4 heterodimer, and three non SMC subunits that probably regulate the complex: dpy-26, capg-1 and dpy-28 (PubMed:19781752, PubMed:19119011, PubMed:18198337). Within the complex, interacts with dpy-26 and smc-4 (PubMed:19781752, PubMed:19119011, PubMed:28301465). Component of the dosage compensation complex, which consist of the condensin I like components mix-1/SMC2 and dpy-27/SMC4, and the three non SMC subunits dpy-26, capg-1 and dpy-28 (PubMed:18198337, PubMed:19781752, PubMed:19119011, PubMed:15557118). Within the complex, interacts with mix-1, dpy-27, dpy-26 and capg-1 (PubMed:15557118, PubMed:18198337, PubMed:19119011, PubMed:28301465). Interacts with smcl-1 (PubMed:28301465). During mitosis, localizes to condensed chromosomes in both sexes. In interphase cells, diffusely distributed in nuclei of hermaphrodite embryos prior to the onset of dosage compensation. Localizes to the X chromosome after the 40-cell stage when dosage compensation is initiated in hermaphrodite (XX) but not in male (X0) embryos, where it remains diffusely nuclear. Expressed in somatic and germline tissues (at protein level). Associates with meiotic and mitotic chromosomes prior to the onset of dosage compensation and with hermaphrodite X chromosomes after the onset of dosage compensation (at protein level). Sumoylated. Sumoylated in the context of the dosage compensation complex but not in the condensin I complex. Sumoylation is important for assembly of the dosage compensation complex and its robust binding to the X chromosome. Results in high larval lethality in hermaphrodites, and survivors exhibit a XX-specific shorter and stouter body morphology (PubMed:18198337). Higher percentage of spontaneous males through X chromosome non-disjunction (PubMed:18198337). Increased number of crossovers, redistribution of crossovers and a reduction in crossover interference in meiosis (PubMed:18198337). Increased number of rad-51 foci in early to mid-pachytene indicating double strand break formation (PubMed:18198337, PubMed:19781752). Increase in X chromosome axis length indicating aberrant chromosome structure (PubMed:19781752). RNAi-mediated knockdown results in chromosome segregation defects in mitosis (PubMed:19119011). Belongs to the CND1 (condensin subunit 1) family.