XYbp, a novel RING-finger protein, is a component of the XY body of spermatocytes and centrosomes.

RING-finger proteins participate in developmental processes, including gametogenesis. A fetal oocyte cDNA library was used to select genes expressed during male germ-cell differentiation. A novel RING-finger protein, XYbp (XY body protein), participating in mouse spermatogenesis has been identified. This novel gene generates a ubiquitously expressed transcript of 4.2 kb and a testis-specific one of 2.8 kb, processed by an alternative polyadenylation mechanism from a non-canonical polyadenylation signal. Transcription of XYbp is regulated during spermatocyte differentiation. The antiserum raised against the XYbp peptide demonstrated that XYbp is localised mainly in the XY bivalent of spermatocytes (XY body) and in the centrosomes of somatic and germ cells in all phases of the cell cycle. These studies indicate that we have identified a new member of the RING-finger family of proteins associated with the XY meiotic bivalent during spermatogenesis development and with the centrosomes of all cells.