Control of O-glycan branch formation. Molecular cloning of human cDNA encoding a novel beta1,6-N-acetylglucosaminyltransferase forming core 2 and core 4.
A novel human UDP-GlcNAc:Gal/GlcNAcbeta1-3GalNAcalpha beta1, 6GlcNAc-transferase, designated C2/4GnT, was identified by BLAST analysis of expressed sequence tags. The sequence of C2/4GnT encoded a putative type II transmembrane protein with significant sequence similarity to human C2GnT and IGnT. Expression of the secreted form of C2/4GnT in insect cells showed that the gene product had UDP-N-acetyl-alpha-D-glucosamine:acceptor beta1, 6-N-acetylglucosaminyltransferase (beta1,6GlcNAc-transferase) activity. Analysis of substrate specificity revealed that the enzyme catalyzed O-glycan branch formation of the core 2 and core 4 type. NMR analyses of the product formed with core 3-para-nitrophenyl confirmed the product core 4-para-nitrophenyl. The coding region of C2/4GnT was contained in a single exon and located to chromosome 15q21.3. Northern analysis revealed a restricted expression pattern of C2/4GnT mainly in colon, kidney, pancreas, and small intestine. No expression of C2/4GnT was detected in brain, heart, liver, ovary, placenta, spleen, thymus, and peripheral blood leukocytes. The expression of core 2 O-glycans has been correlated with cell differentiation processes and cancer. The results confirm the predicted existence of a beta1,6GlcNAc-transferase that functions in both core 2 and core 4 O-glycan branch formation. The redundancy in beta1,6GlcNAc-transferases capable of forming core 2 O-glycans is important for understanding the mechanisms leading to specific changes in core 2 branching during cell development and malignant transformation.
Schwientek
T
T
School of Dentistry, University of Copenhagen, Norre Allé 20, 2200 Copenhagen N, Denmark.
Nomoto
M
M
Levery
S B
SB
Merkx
G
G
van Kessel
A G
AG
Bennett
E P
EP
Hollingsworth
M A
MA
Clausen
H
H
D000595:Amino Acid Sequence; D001483:Base Sequence; D002884:Chromosomes, Human, Pair 15; D003001:Cloning, Molecular; D018076:DNA, Complementary; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases / Q000737:chemistry / Q000235:genetics*; D011134:Polysaccharides / Q000737:chemistry*; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid