A FAMILY OF HUMAN BETA-3-GALACTOSYLTRANSFERASES - CHARACTERIZATION OF4 MEMBERS OF A UDP-GALACTOSE-BETA-N-ACETYL-GLUCOSAMINE BETA-N-ACETYL-GALACTOSAMINE BETA-1,3-GALACTOSYLTRANSFERASE FAMILY/

BLAST analysis of expressed sequence tags (ESTs) using the coding sequ ence of a human UDP-galactose:beta-N-acetyl-glucosamine beta-1,3-galac tosyltransferase, designated beta 3Gal-T1, revealed no ESTs with ident ical sequences but a large number with similarity. Three different set s of overlapping ESTs with sequence similarities to beta 3Gal-T1 were compiled, and complete coding regions of these genes were obtained Exp ression of two of these genes in the Baculo virus system showed that o ne represented a UDP-galactose:beta-N-acetylglucosamine beta-1,3-galac tosyltransferase (beta 3Gal-T2) with similar kinetic properties as bet a 3Gal-T1. Another gene represented a UDP-galactose:beta-N-acetyl-gala ctosamine beta-1,3-galactosyltransferase (beta 3Gal-T4) involved in G( M1)/G(D1) ganglioside synthesis, and this gene was highly similar to a recently reported rat G(D1) synthase (Miyazaki,H., Fukumoto, S., Okad a, M., Hasegawa, T., and Furukawa, K. (1997) J. Biol. Chem. 272, 24794 -24799), Northern analysis of mRNA from human organs with the four hom ologous cDNA revealed different expression patterns. beta 3Gal-T1 mRNA was expressed in brain, beta 3Gal-T2 was expressed in brain and heart , and beta 3Gal-T3 and -T4 were more widely expressed. The coding regi ons for each of the four genes were contained in single exons. beta 3G al-T2, -T3, and -T4 were localized to 1q31, 3q25, and 6p21.3, respecti vely, by EST mapping. The results demonstrate the existence of a famil y of homologous beta 3-galactosyltransferase genes.