Cloning, expression and gene organization of a human Neu5Ac alpha 2-3Gal beta 1-3GalNAc alpha 2,6-sialyltransferase: hST6GalNAcIV.
On the basis of the detection of expressed sequence tag ('EST') similar to the rat N-acetylgalactosamine alpha2,6-sialyltransferase (ST6GalNAc) III cDNA, we have identified a novel member of the human ST6GalNAc family. We have isolated a cDNA clone containing an open reading frame that codes for a type II membrane protein of 302 amino acids with a seven-amino-acid cytoplasmic domain, an 18-amino-acid transmembrane domain and the smallest described catalytic domain of 277 amino acids. This predicted sialyltransferase sequence is similar to the rat ST6GalNAc III (46.6%), but was found to be even more similar to the recently reported mouse ST6GalNAc IV (88.1%) on the basis of amino acid sequence identity. Northern-blot analysis showed that the newly identified gene is expressed constitutively in various adult human tissues as a 2.2kb transcript, but was also found to be expressed at lower levels in brain, heart and skeletal muscle as a 2.5kb transcript. Expression of the hST6GalNAc IV gene was investigated by reverse transcription PCR in various human cancer cells, and was found to be present in the majority of cell types with the exception of the carcinoma cell line T47D and pro-monocyte THP cells. The transient expression in COS-7 cells of the full-length cDNA led to the production of an active enzyme sharing the acceptor specificity of the ST6GalNAc family towards Neu5Ac alpha 2-3Gal beta 1-3GalNAc alpha-O-R (where 'R' denotes H, benzyl, or a peptidic chain). Detailed analysis in vitro of substrate specificity revealed that the enzyme required the trisaccharide Neu5Ac alpha 2-3Gal beta1-3GalNAc found on O-glycans and arylglycosides. In addition, we have clarified the genomic organization of ST6GalNAc IV gene.
Harduin-Lepers
A
A
Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS n8576, Laboratoire de Chimie Biologique, Université des Sciences et Technologies de Lille, F-59655 Villeneuve d'Ascq, France.
Stokes
D C
DC
Steelant
W F
WF
Samyn-Petit
B
B
Krzewinski-Recchi
M A
MA
Vallejo-Ruiz
V
V
Zanetta
J P
JP
Augé
C
C
Delannoy
P
P
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D019556:COS Cells; D020134:Catalytic Domain; D002899:Chromosomes, Human, Pair 9; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D020224:Expressed Sequence Tags; D005455:Fluorescent Antibody Technique; D006801:Humans; D007700:Kinetics; D051379:Mice; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D012799:Sialyltransferases / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D013379:Substrate Specificity; D014018:Tissue Distribution; D014162:Transfection; D014407:Tumor Cells, Cultured
D018076:DNA, Complementary; D011994:Recombinant Proteins; D012313:RNA; D012799:Sialyltransferases; C485573:ST6GALNAC4 protein, human; C118899:Siat7d protein, mouse