Transcriptional regulation of the human ST6GAL2 gene in cerebral cortex and neuronal cells.
The second human beta-galactoside alpha-2,6-sialyltransferase (hST6Gal II) differs from hST6Gal I, the first member of ST6Gal family, in substrate specificity and tissue expression pattern. While ST6GAL1 gene is expressed in almost all human tissues, ST6GAL2 shows a restricted tissue-specific pattern of expression, mostly expressed in embryonic and adult brain. In order to understand the mechanisms involved in the transcriptional regulation of ST6GAL2, we first characterized the transcription start sites (TSS) in SH-SY5Y neuroblastoma cells. 5' RACE experiments revealed multiple TSS located on three first alternative 5' exons, termed EX, EY and EZ, which are unusually close on the genomic sequence and are all located more than 42 kbp upstream of the first common coding exon. Using Taqman duplex Q-PCR, we showed that the ST6GAL2 transcripts initiated by EX or EY are mainly expressed in both brain-related cell lines and human cerebral cortex, testifying for the use of a similar transcriptional regulation in vivo. Furthermore, we also showed for the first time hST6Gal II protein expression in the different lobes of the human cortex. Luciferase reporter assays allowed us to define two sequences upstream EX and EY with a high and moderate promoter activity, respectively. Bioinformatics analysis and site-directed mutagenesis showed that NF-kappaB and NRSF are likely to act as transcriptional repressors, whereas neuronal-related development factors Sox5, Puralpha and Olf1, are likely to act as transcriptional activators of ST6GAL2. This suggests that ST6GAL2 transcription could be potentially activated for specific neuronal functions.
Lehoux
Sylvain
S
Structural and Functional Glycobiology Unit, UMR CNRS 8576, University of Sciences and Technologies of Lille, 59655, Villeneuve d'Ascq, France.
Groux-Degroote
Sophie
S
Cazet
Aurélie
A
Dhaenens
Claire-Marie
CM
Maurage
Claude-Alain
CA
Caillet-Boudin
Marie-Laure
ML
Delannoy
Philippe
P
Krzewinski-Recchi
Marie-Ange
MA
D020121:5' Untranslated Regions / Q000235:genetics; D020029:Base Pairing / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D045744:Cell Line, Tumor; D002540:Cerebral Cortex / Q000201:enzymology*; D019295:Computational Biology; D057075:Enzyme Assays; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009474:Neurons / Q000201:enzymology*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012799:Sialyltransferases / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
D020121:5' Untranslated Regions; D008156:Luciferases; D012333:RNA, Messenger; D012799:Sialyltransferases; D014157:Transcription Factors; C549032:ST6GAL2 protein, human