By yeast 2-hybrid screen using Tex15 as bait, Yang et al. (2007) cloned mouse Ubl4b. The deduced 188-amino acid protein contains a 72-amino acid ubiquitin domain. RT-PCR and Western blot analysis detected Ubl4b mRNA and protein only in mouse testis. Immunofluorescence analysis revealed Ubl4b in the cytoplasm of elongated spermatids, but not in spermatocytes, round spermatids, Leydig cells, or Sertoli cells, suggesting Ubl4b functions in late spermiogenesis. By database analysis, Yang et al. (2007) identified human UBL4B and several mammalian orthologs.

Yang et al. (2007) stated that the mouse Ubl4b gene maps to chromosome 3 and that the human UBL4B gene is in a syntenic region where it is flanked by ALX3 and SLC6A17 on chromosome 1p13.3.