Homology Of A Candidate Spermatogenic Gene From The Mouse Y-chromosome To The Ubiquitin-activating Enzyme-e1

Abstract

THE Sxr (sex-reversed) region, a fragment of the Y chromosome short arm, can cause chromosomally female XXSxr or XSxrO mice to develop as sterile males 1-3. The original Sxr region, termed Sxr(a), encodes: Tdy, the primary sex-determining gene; Hya, the controlling or structural locus for the minor transplantation antigen H-Y (ref. 4); gene(s) controlling the expression of the serologically detected male antigen (SDMA) 5; Spy, a gene(s) required for the survival and proliferation of A spermatogonia during spermatogenesis 6,7; Zfy-1/Zfy-2, zinc-finger-containing genes of unknown function 8; and Sry, which is probably identical to Tdy (ref. 9). A deletion variant 10 of Sxr(a), termed Sxr(b), which lacks Hya, SDMA expression, Spy and some Zfy-2 sequences, makes positional cloning of these genes possible. We report here the isolation of a new testis-specific gene, Sby, mapping to the DNA deleted from the Sxr(b) region (the DELTA-Sxr(b) interval). Sby has extensive homology to the X-linked human ubiquitin-activating enzyme E1 (ref. 11). The critical role of this enzyme in nuclear DNA replication 12 together with the testis-specific expression of Sby suggests Sby as a candidate for the spermatogenic gene Spy.