COMPLETE SEQUENCE OF THE OVINE BETA-CASEIN-ENCODING GENE AND INTERSPECIES COMPARISON

The 9149-bp transcription unit encoding ovine beta-casein (Gas) and 46 36 bp of 5' flanking region were completely sequenced. The gene is com posed of nine exons and its overall organization is similar to that of its counterparts from other species. Intron 4, the largest, shares th ree similar stretches (sizes ranging from 0.1 to 0.3 kb) with the regi on upstream from the transcription unit. These common sequences are pa rt of short interspersed nuclear elements (SINE) specific to Bovidne ( Bov). Intron 4 contains two 274-bp Bov-A2 SINE in opposite orientation , as well as a full-length 569-bp Bov-B SINE. This latter SINE, also p resent in caprine intron 4, is missing in cattle. This suggests that t he amplification of Bov-SINE has continued after the divergence of cat tle from sheep and goats, assuming that the presently known sequences are representative of these species.