Histones H1 are necessary for the condensation of nucleosome chains into higher-order structures (Probable) (PubMed:23028351). Probably does not act as global transcriptional repressor (PubMed:23028351). Acting in concert with chromobox protein homologs hpl-1 and hpl-2, involved in reproduction, somatic gonad development, male tail development, and vulval cell fate decisions; perhaps as a result of modulating expression of Hox genes mab-5 and egl-5 (PubMed:23028351). Plays a role in linking epigenetic regulation with the innate immune response (PubMed:22083954). Interacts with nmad-1 (PubMed:31283754). Interacts (when monomethylated at Lys-14) with chromobox protein homolog hpl-1; the interaction is direct (PubMed:23028351). Interacts (when monomethylated at Lys-14) with histone H3 (when trimethylated on 'Lys-27'); the interaction is direct (PubMed:23028351). Cytoplasmic localization is observed after infection with Gram-positive bacterium B.thuringiensis. Methylation at lysine 14 is necessary to regulate male tail development. Belongs to the histone H1/H5 family.