A4GNT | GeneID:51146 | Homo sapiens
[ ] NCBI Entrez Gene
|Gene ID||51146||Official Symbol||A4GNT|
|Also Known As|
|Summary||This gene encodes a protein from the glycosyltransferase 32 family. The enzyme catalyzes the transfer of N-acetylglucosamine (GlcNAc) to core 2 branched O-glycans. It forms a unique glycan, GlcNAcalpha1-->4Galbeta-->R and is largely associated with the Golgi apparatus membrane. [provided by RefSeq]|
Orthologs and Paralogs
|GeneID:485683||A4GNT||XP_542803.2||Canis lupus familiaris|
[ ] Monoclonal and Polyclonal Antibodies
|1||sigma||HPA008017||Anti-A4GNT antibody produced in rabbit ;|
|GO:0016021||Component||integral to membrane|
|GO:0016757||Function||transferase activity, transferring glycosyl groups|
|GO:0005975||Process||carbohydrate metabolic process|
|GO:0009101||Process||glycoprotein biosynthetic process|
|GO:0006493||Process||protein amino acid O-linked glycosylation|
MicroRNA and Targets
[ ] MicroRNA Sequences and Transcript Targets from miRBase at Sanger
|RNA Target||miRNA #||mat miRNA||Mature miRNA Sequence|
- [ ] Barbe L, et al. (2008) "Toward a confocal subcellular atlas of the human proteome." Mol Cell Proteomics. 7(3):499-508. PMID:18029348
- [ ] Ishizone S, et al. (2006) "Clinical utility of quantitative RT-PCR targeted to alpha1,4-N-acetylglucosaminyltransferase mRNA for detection of pancreatic cancer." Cancer Sci. 97(2):119-126. PMID:16441422
- [ ] Gerhard DS, et al. (2004) "The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC)." Genome Res. 14(10B):2121-2127. PMID:15489334
- [ ] Shimizu F, et al. (2003) "Usefulness of the real-time reverse transcription-polymerase chain reaction assay targeted to alpha1,4-N-acetylglucosaminyltransferase for the detection of gastric cancer." Lab Invest. 83(2):187-197. PMID:12594234
- [ ] Strausberg RL, et al. (2002) "Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences." Proc Natl Acad Sci U S A. 99(26):16899-16903. PMID:12477932
- [ ] Zhang MX, et al. (2001) "Immunohistochemical demonstration of alpha1,4-N-acetylglucosaminyltransferase that forms GlcNAcalpha1,4Galbeta residues in human gastrointestinal mucosa." J Histochem Cytochem. 49(5):587-596. PMID:11304796
- [ ] Nakayama J, et al. (1999) "Expression cloning of a human alpha1, 4-N-acetylglucosaminyltransferase that forms GlcNAcalpha1-->4Galbeta-->R, a glycan specifically expressed in the gastric gland mucous cell-type mucin." Proc Natl Acad Sci U S A. 96(16):8991-8996. PMID:10430883
- [ ] Suzuki Y, et al. (1997) "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library." Gene. 200(1-2):149-156. PMID:9373149
- [ ] Maruyama K, et al. (1994) "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides." Gene. 138(1-2):171-174. PMID:8125298
Information on protein localization on the subcellular level is important to map and characterize the proteome and to better understand cellular functions of proteins. Here we report on a pilot study of 466 proteins in three human cell lines aimed to allow large scale confocal microscopy analysis using protein-specific antibodies. Approximately 3000 high resolution images were generated, and more than 80% of the analyzed proteins could be classified in one or multiple subcellular compartment(s). The localizations of the proteins showed, in many cases, good agreement with the Gene Ontology localization prediction model. This is the first large scale antibody-based study to localize proteins into subcellular compartments using antibodies and confocal microscopy. The results suggest that this approach might be a valuable tool in conjunction with predictive models for protein localization.
alpha1,4-N-Acetylglucosaminyltransferase (alpha4GnT) is a glycosyltransferase responsible for the biosynthesis of alpha1,4-GlcNAc-capped O-glycans, and is frequently expressed in pancreatic cancer cells but not peripheral blood cells. In the present study, we tested the clinical utility of alpha4GnT mRNA expressed in the mononuclear cell fraction of peripheral blood as a biomarker of pancreatic cancer. Total RNA isolated from the peripheral blood mononuclear cells from 55 pancreatic cancer patients, 10 chronic pancreatitis patients, and 70 cancer-free volunteers was analyzed quantitatively by reverse transcription-polymerase chain reaction with primers specific for alpha4GnT, and the expression level of alpha4GnT mRNA relative to that of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was measured. When the ratio of alpha4GnT to GAPDH transcripts exceeded a defined cut-off value, patients were considered to have pancreatic cancer. By these standards, 76.4% of the pancreatic cancer patients were detected by this assay. A strong correlation was obtained between positivity in this assay and the expression of alpha4GnT protein detected immunohistochemically in pancreatic cancer tissues resected subsequently, suggesting that alpha4GnT mRNA detected in the peripheral blood is derived from circulating pancreatic cancer cells. Although increased levels of alpha4GnT mRNA was detected in 40.0% of chronic pancreatitis patients and 17.1% of cancer-free volunteers, the expression levels were significantly lower than those seen in pancreatic cancer patients. These results suggest that quantitative analysis of alpha4GnT mRNA expressed in the mononuclear cell fraction of peripheral blood will contribute to the detection of pancreatic cancer.
The National Institutes of Health's Mammalian Gene Collection (MGC) project was designed to generate and sequence a publicly accessible cDNA resource containing a complete open reading frame (ORF) for every human and mouse gene. The project initially used a random strategy to select clones from a large number of cDNA libraries from diverse tissues. Candidate clones were chosen based on 5'-EST sequences, and then fully sequenced to high accuracy and analyzed by algorithms developed for this project. Currently, more than 11,000 human and 10,000 mouse genes are represented in MGC by at least one clone with a full ORF. The random selection approach is now reaching a saturation point, and a transition to protocols targeted at the missing transcripts is now required to complete the mouse and human collections. Comparison of the sequence of the MGC clones to reference genome sequences reveals that most cDNA clones are of very high sequence quality, although it is likely that some cDNAs may carry missense variants as a consequence of experimental artifact, such as PCR, cloning, or reverse transcriptase errors. Recently, a rat cDNA component was added to the project, and ongoing frog (Xenopus) and zebrafish (Danio) cDNA projects were expanded to take advantage of the high-throughput MGC pipeline.
alpha1,4-N-acetylglucosaminyltransferase (alpha4GnT) is a glycosyltransferase that forms a unique glycan, GlcNAcalpha1-->4Galbeta-->R, specifically present in gastric gland mucous cell-type mucin. Recently, we molecularly cloned human alpha4GnT and showed that alpha4GnT is expressed in the mucous cells that secrete this particular mucin. In the present study, we first demonstrated that alpha4GnT was frequently expressed in gastric cancer cells but not in peripheral blood cells using immunohistochemistry. To detect gastric cancer cells circulating in the peripheral blood of gastric cancer patients, we quantitatively analyzed the expression level of alpha4GnT mRNA in the mononuclear cell fraction of peripheral blood using real-time reverse transcription polymerase chain reaction. The transcripts of alpha4GnT were detected in the mononuclear cell fraction isolated from 62.2% of 37 gastric cancer patients but not from any of 23 healthy individuals. Significant correlation was found in the expression levels of alpha4GnT mRNA in peripheral blood and alpha4GnT protein in gastric cancer cells. Surprisingly, alpha4GnT mRNA was detectable in 80% of five patients with an early stage of gastric cancer when the cancer cells were limited to the gastric mucosa, and the expression levels of alpha4GnT mRNA were increased in association with tumor progression. In three patients with gastric cancer, during postsurgical follow-up, the expression levels of alpha4GnT mRNA were decreased after surgical removal of gastric cancer. However, significant amounts of the alpha4GnT transcripts were again detected in two patients, who eventually developed to the recurrence of gastric cancer. Although alpha4GnT was detected in 33.3% of nine patients with Helicobacter pylori-infected chronic active gastritis as well as all of four patients with peptic ulcer, the mean expression level of alpha4GnT mRNA in these benign disorders was lower than that in gastric cancer. These results altogether indicate that the quantitative analysis of alpha4GnT mRNA expressed in the peripheral blood is useful for the detection and, possibly, monitoring of gastric cancer.
The National Institutes of Health Mammalian Gene Collection (MGC) Program is a multiinstitutional effort to identify and sequence a cDNA clone containing a complete ORF for each human and mouse gene. ESTs were generated from libraries enriched for full-length cDNAs and analyzed to identify candidate full-ORF clones, which then were sequenced to high accuracy. The MGC has currently sequenced and verified the full ORF for a nonredundant set of >9,000 human and >6,000 mouse genes. Candidate full-ORF clones for an additional 7,800 human and 3,500 mouse genes also have been identified. All MGC sequences and clones are available without restriction through public databases and clone distribution networks (see http:mgc.nci.nih.gov).
alpha1,4-N-acetylglucosaminyltransferase (alpha4GnT) is a glycosyltransferase that mediates transfer of GlcNAc to betaGal residues with alpha1,4-linkage, forming GlcNAcalpha1--> 4Galbeta-->R structures. In normal human tissues, glycoproteins having GlcNAcalpha1-->4Galbeta-->R structures at non-reducing terminals are exclusively limited to the mucins secreted from glandular mucous cells of gastric mucosa, Brunner's gland of duodenum, and accessory gland of pancreaticobiliary tract. Recently, we have isolated a cDNA encoding human alpha4GnT by expression cloning. Although alpha4GnT plays a key role in producing this unique glycan in vitro, the actual localization of alpha4GnT was not determined. In this study we examined the localization of alpha4GnT in various human tissues, including gastrointestinal mucosa, using a newly developed antibody against human alpha4GnT. The specificity of the antibody was confirmed by analyses of human gastric adenocarcinoma AGS cells transfected by alpha4GnT cDNA. Expression of alpha4GnT was largely associated with the Golgi region of mucous cells that produce the mucous glycoproteins having GlcNAcalpha1-->4Galbeta-->R, such as the glandular mucous cells of stomach and Brunner's gland. An immunoprecipitation experiment disclosed that two distinct mucin proteins, MUC5AC and MUC6 present in gastric mucin, carried the GlcNAcalpha1-->4Galbeta-->R structures. These results indicate that alpha4GnT is critical to form the mucous glycoproteins having GlcNAcalpha1-->4Galbeta-->R on MUC6 and MUC5AC in vivo.(J Histochem Cytochem 49:587-596, 2001)
Among mucus-secreting cells, the gastric gland mucous cells, Brunner's glands, accessory glands of pancreaticobiliary tract, and pancreatic ducts exhibiting gastric metaplasia are unique in that they express class III mucin identified by paradoxical Con A staining composed of periodate oxidation, sodium borohydride reduction, Con A, and horseradish peroxidase reaction. Recently it was shown that these mucous cells secrete glycoproteins having GlcNAcalpha1-->4Galbeta-->R at nonreducing terminals of the carbohydrate moieties. Herein we describe the expression cloning of a cDNA encoding a human alpha1,4-N-acetylglucosaminyltransferase (alpha4GnT), a key enzyme for the formation of GlcNAcalpha1-->4Galbeta1-->R. COS-1 cells were thus cotransfected with a stomach cDNA library and a leukosialin cDNA. Transfected COS-1 cells were screened by using monoclonal antibodies specific for GlcNAcalpha1-->4Galbeta-->R and enriched by fluorescence-activated cell sorting. Sibling selection of recovered plasmids resulted in a cDNA clone that directs the expression of GlcNAcalpha1-->4Galbeta-->R. The deduced amino acid sequence predicts a type II membrane protein with 340 amino acids, showing no significant similarity with any other proteins. The alpha4GnT gene is located at chromosome 3p14.3, and its transcripts are expressed in the stomach and pancreas. An in vitro GlcNAc transferase assay by using a soluble alpha4GnT revealed that alpha1,4-linked GlcNAc residues are transferred most efficiently to core 2 branched O-glycans (Galbeta1-->4GlcNAcbeta1-->6(Galbeta1-->3)GalNAc), forming GlcNAcalpha1-->4Galbeta1-->4GlcNAcbeta1-->6(GlcNAca lpha1-->4Galbeta1- ->3)GalNAc. Transfection of alpha4GnT cDNA into gastric adenocarcinoma AGS cells produced class III mucin, indicating that alpha4GnT is responsible for the formation of class III Con A reactivity. These results indicate that the alpha4GnT is a glycosyltransferase that forms alpha1,4-linked GlcNAc residues, preferentially in O-glycans.
Using 'oligo-capped' mRNA [Maruyama, K., Sugano, S., 1994. Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides. Gene 138, 171-174], whose cap structure was replaced by a synthetic oligonucleotide, we constructed two types of cDNA library. One is a 'full length-enriched cDNA library' which has a high content of full-length cDNA clones and the other is a '5'-end-enriched cDNA library', which has a high content of cDNA clones with their mRNA start sites. The 5'-end-enriched library was constructed especially for isolating the mRNA start sites of long mRNAs. In order to characterize these libraries, we performed one-pass sequencing of randomly selected cDNA clones from both libraries (84 clones for the full length-enriched cDNA library and 159 clones for the 5'-end-enriched cDNA library). The cDNA clones of the polypeptide chain elongation factor 1 alpha were most frequently (nine clones) isolated, and more than 80% of them (eight clones) contained the mRNA start site of the gene. Furthermore, about 80% of the cDNA clones of both libraries whose sequence matched with known genes had the known 5' ends or sequences upstream of the known 5' ends (28 out of 35 for the full length-enriched library and 51 out of 62 for the 5'-end-enriched library). The longest full-length clone of the full length-enriched cDNA library was about 3300 bp (among 28 clones). In contrast, seven clones (out of the 51 clones with the mRNA start sites) from the 5'-end-enriched cDNA library came from mRNAs whose length is more than 3500 bp. These cDNA libraries may be useful for generating 5' ESTs with the information of the mRNA start sites that are now scarce in the EST database.
We have devised a method to replace the cap structure of a mRNA with an oligoribonucleotide (r-oligo) to label the 5' end of eukaryotic mRNAs. The method consists of removing the cap with tobacco acid pyrophosphatase (TAP) and ligating r-oligos to decapped mRNAs with T4 RNA ligase. This reaction was made cap-specific by removing 5'-phosphates of non-capped RNAs with alkaline phosphatase prior to TAP treatment. Unlike the conventional methods that label the 5' end of cDNAs, this method specifically labels the capped end of the mRNAs with a synthetic r-oligo prior to first-strand cDNA synthesis. The 5' end of the mRNA was identified quite simply by reverse transcription-polymerase chain reaction (RT-PCR).