Regulated expression of the ubiquitin protein ligase, E3 Histone /LASU1/Mule/ARF‐BP1/HUWE1, during spermatogenesis

A ubiquitin protein ligase (E3), E3 Histone /LASU1 (Mule/ARF‐BP1/HUWE1), was recently identified that mediates ubiquitination of core histones, the Mcl‐1 anti‐apoptotic protein, and the p53 tumor suppressor protein. However, the expression of E3 Histone /LASU1 remains poorly studied. Because we identified E3 Histone /LASU1 from the testis, we explored its regulation during spermatogenesis. In the first wave of rat spermatogenesis, E3 Histone /LASU1 mRNA and protein had peak expression at days 10 and 20, respectively, and decreased with age. Consistent with these findings, immunohistochemistry revealed that E3 Histone /LASU1 was highly expressed in nuclei from spermatogonia to mid‐pachytene spermatocytes. There was no obvious staining in spermatids, when histones are ubiquitinated and degraded. E3 Histone /LASU1 was also expressed in other tissues. However, except in neuronal cells of the brain, expression was cytoplasmic. Thus, E3 Histone /LASU1 may play a role in chromatin modification in early germ cells of the testis, but also has functions in other tissues. Developmental Dynamics 236:2889–2898, 2007. © 2007 Wiley‐Liss, Inc.