Rnf19a,a ubiquitin protein ligase,and Psmc3, a component of the 26S proteasome,Tether to the acrosome membranes and the head–tail coupling apparatus during rat spermatid development

We report the cDNA cloning of rat testis Rnf19a, a ubiquitin protein ligase, and show 98% and 93% protein sequence identity of testicular mouse and human Rnf19a, respectively. Rnf19a interacts with Psmc3, a protein component of the 19S regulatory cap of the 26S proteasome. During spermatid development, Rnf19a and Psmc3 are initially found in Golgi‐derived proacrosomal vesicles. Later on, Rnf19a, Psmc3, and ubiquitin are seen along the cytosolic side of the acrosomal membranes and the acroplaxome, a cytoskeletal plate linking the acrosome to the spermatid nuclear envelope. Rnf19a and Psmc3 accumulate at the acroplaxome marginal ring–manchette perinuclear ring region during spermatid head shaping and in the developing sperm head–tail coupling apparatus and tail. Rnf19a and Psmc3 may interact directly or indirectly with each other, presumably pointing to the participation of the ubiquitin–proteasome system in acrosome biogenesis, spermatid head shaping, and development of the head‐tail coupling apparatus and tail. Developmental Dynamics 238:1851–1861, 2009. © 2009 Wiley‐Liss, Inc.