Molecular cloning, expression and exon/intron organization of the bovine beta-galactoside alpha2,6-sialyltransferase gene.
In this study, we report the first isolation and characterization of a bovine sialyltransferase gene. Bovine cDNAs prepared from different tissues contain an open-reading frame encoding a 405 amino acid sequence showing 83%, 75%, and 60% identity with human, murine, and chicken ST6Gal I (beta-galactoside alpha2,6-sialyltransferase) sequences, respectively. When transfected into COS-7 cells, a recombinant enzyme was obtained which catalyzed the in vitro alpha2, 6-sialylation of LacNAc (NeuAcalpha2-6Galbeta1-4GlcNAc) and LacdiNAc (NeuAcalpha2-6GalNAcbeta1-4GlcNAc) acceptor substrates. The K (m) values were 2.8 and 6.9 mM, respectively. Different relative efficiencies (Vmax/Km) for the two precursors (36 for LacNAc and 4.3 for LacdiNAc) were observed. Bovine ST6Gal I gene consists of four 5'-untranslated exons E(-2) to E(1), and five coding exons from E(2) to E(6). This later carries a 3'-untranslated region of 2. 7 kb. Gene sequence spans at least 80 kb of genomic DNA. Two processed pseudogenes have been identified. They are 94.3 and 95.6% similar to the bovine cDNA, respectively. Three families of mRNA isoforms were isolated. They differed by their 5'-untranslated regions and could be generated by three tissue-specific promoters. Family 1 is made up of exons E(-2) and E(1) to E(6), family 2 of exons E(-1) to E(6), and family 3 of exons E(1) to E(6). Tissular distribution of transcript families appears noticeably different than those described in human and rat.
Mercier
D
D
Institut de Biotechnologie, Faculté des Sciences, Université de Limoges, 87060 Limoges, France.
Wierinckx
A
A
Oulmouden
A
A
Gallet
P F
PF
Palcic
M M
MM
Harduin-Lepers
A
A
Delannoy
P
P
Petit
J M
JM
Levéziel
H
H
Julien
R
R
D020121:5' Untranslated Regions; D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD; D001483:Base Sequence; D002417:Cattle; D003001:Cloning, Molecular; D005091:Exons; D015971:Gene Expression Regulation, Enzymologic; D007438:Introns; D008969:Molecular Sequence Data; D011544:Pseudogenes; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis; D018626:Retroelements; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012799:Sialyltransferases / Q000235:genetics*; D013379:Substrate Specificity; D014018:Tissue Distribution; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
D020121:5' Untranslated Regions; D015703:Antigens, CD; D012333:RNA, Messenger; D011994:Recombinant Proteins; D018626:Retroelements; D012799:Sialyltransferases; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase