DNA-binding protein that may be implicated in chromatin remodeling and/or transcriptional regulation during spermiogenesis, the process of spermatid maturation into spermatozoa. Expressed exclusively in the testis. Belongs to the histone H1/H5 family. Could be the product of a pseudogene. However, mouse (AC Q9QYL0) and rat (AC D3ZZW6) orthologs encode functional proteins.