Organization of the bovine alpha 2-fucosyltransferase gene cluster suggests that the Sec1 gene might have been shaped through a nonautonomous L1-retrotransposition event within the same locus

By referring to the split coding sequence of the highly conserved alpha6-fu cosyltransferase gene family (assumed to be representative of the common al pha2 and alpha6 fucosyltransferase gene ancestor), we have hypothesized tha t the monoexonic coding sequences of the present alpha2-fucosyltransferase genes have been shaped in mammals by several events of retrotransposition a nd/or duplication. In order to test our hypothesis, we determined the struc ture of the three bovine alpha2-fucosyltransferase genes (bfut1, bfut2, and sec1) and analyzed their characteristics compared with their human counter parts (FUT1, FUT2, and Sec1). We show that in mammals, a complex nonautonom ous L1-retrotransposition event occurred within the locus of the alpha2-fuc osyltransferase ancestor gene itself. A consequence of this event was the p rocessing in Catarrhini of a Sec1 pseudogene via several point mutations.