Seems to be involved in transcriptional silencing in heterochromatin-like complexes (PubMed:11850401). Probably does not act as global transcriptional repressor, instead targeting a subset of genes (PubMed:23028351, PubMed:19064713, PubMed:22185090, PubMed:25467431). Involved in RNA processing mediated by Tar DNA-binding protein homolog tdp-1 (PubMed:29760282). Plays a role in linking epigenetic regulation with the innate immune response (PubMed:22083954). Involved in the endoplasmic reticulum (ER) stress response via modulation of the unfolded protein response (UPR), acting mainly through the IRE1-XBP1 pathway and perhaps, to a lesser extent, through the autophagy pathway (PubMed:24715729). May act in a common pathway with retinoblastoma-like protein homolog lin-35 and zinc finger protein lin-13 to influence the ER stress response in the intestine (PubMed:24715729). Plays a role in the formation of the vulva and in fertility, acting together with a CoREST-like complex, and chromobox protein homolog hpl-1 (PubMed:26476455, PubMed:16905130, PubMed:16890929, PubMed:11850401). Acting in concert with hpl-1 and histone H1 protein his-24, involved in reproduction, somatic gonad development, male tail development and vulval cell fate specification; perhaps as a result of modulating expression of Hox genes mab-5 and egl-5 (PubMed:23028351, PubMed:16905130, PubMed:16890929, PubMed:11850401, PubMed:19064713). In vulval cell fate specification may act by repressing transcription, of EGF family gene lin-3 in hypodermal hyp7, and of homeobox lin-39 in vulval precursor cells (VPC) (PubMed:19064713). Role in growth and somatic gonad development is antagonized by histone-lysine N-methyltransferase set-2/SET1 (PubMed:17967446). Required for larval development, acting redundantly with hpl-1 (PubMed:16905130). Plays a role in regulation of the developmentally arrested larval state known as dauer, longevity, and lipid metabolism (PubMed:22185090). Interacts with histone H3 when di-, or tri-methylated at 'Lys-27' (H3K27me2/me3), or tri-methylated at 'Lys-9' (H3K9me3) (PubMed:26476455, PubMed:23028351). Interacts with Tar DNA-binding protein homolog tdp-1; interaction may maintain localization of hpl-2 to gene bodies (PubMed:29760282). Interacts with histone H1 his-24, probably via interaction with hpl-1 (PubMed:22083954). Interacts with chromobox protein homolog hpl-1 (PubMed:22083954). May form homodimers (PubMed:16890929). Interacts (via chromo (shadow subtype) domain) with zinc finger protein lin-13 (via PLVPV motif); the interaction is direct and influences localization of hpl-2 to nuclear foci (PubMed:16890929). Localizes to distinct nuclear foci, not overlapping significantly with hpl-1, in embryonic cells (PubMed:26476455, PubMed:16905130). Localization to nuclear foci overlaps partially with zinc finger protein lin-13 (PubMed:16890929). Localizes to foci in a lin-13-dependent manner (PubMed:16890929). Localization along chromosomal arms correlates with localization of histone H3 methylated at 'Lys-9' (H3K9me), however, hpl-2 can associate with chromatin in an H3K9me-independent manner (PubMed:25467431). Localization on chromosome correlates with sequences enriched in repetitive elements, or in well-expressed genes (PubMed:25467431). Localized to gene bodies (PubMed:29760282). Expressed in embryos at about the 20-50 cell stage (PubMed:11850401, PubMed:16905130). Expression persists throughout development and into adulthood (PubMed:11850401). Also expressed at lower level in germ cells, developing oocytes and embryos starting at the two-cell stage, before the onset of zygotic transcription, suggesting that the protein is maternally inherited (PubMed:11850401). Expressed in hyp7 hypodermal cells and vulval precursor cells of larval L2 stage hermaphrodites (PubMed:19064713). Causes ectopic up-regulation of transcription of specific genes, such as lin-39 and lag-2 (PubMed:16890929). Causes accumulation of double-stranded RNA transcripts (PubMed:29760282). Splicing defects (PubMed:29760282). Results in increased levels of spliced xbp-1 under basal conditions (PubMed:24715729). Increases survival in response to ER stress inducers tunicamycin or dithiothreitol (DTT), as compared to wild-type (PubMed:24715729). Knockout in a chromobox protein homolog hpl-1 mutant background has no effect on the distribution of monomethylated histone H3 'Lys-9' (H3K9me3) in chromatin (PubMed:26476455). Germline nuclei differ in size and morphology in a his-24 mutant background, probably as a result of altered chromatin compaction (PubMed:23028351). Causes defects in gonad elongation when grown at 25 degrees Celsius; phenotype exacerbated in an hpl-1 mutant background (PubMed:16905130). Causes vulva defects, infertility and larval lethality, in particular when grown at 25 degrees Celsius; exacerbated in various mutant backgrounds, such as hpl-1, or rcor-1 or his-24, or by simultaneous RNAi-mediated knockdown of lin-15A, or lin-9 or lin-35 (PubMed:26476455, PubMed:23028351, PubMed:16890929). Causes male tail defects in a his-24 mutant background (PubMed:23028351). Some knockout phenotypes are suppressed by simultaneous RNAi-mediated knockdown of histone-lysine N-methyltransferase set-2 (PubMed:17967446). RNAi-mediated knockdown causes sterility and vulval defects; sterility exacerbated by simultaneous RNAi-mediated knockdown of hpl-1. Defects in oocyte morphology, perhaps due to abnormal maturation (PubMed:11850401).