Chromosome mapping and organization of the human beta-galactoside alpha 2,6-sialyltransferase gene. Differential and cell-type specific usage of upstream exon sequences in B-lymphoblastoid cells.
The human beta-galactoside alpha 2,6-sialyltransferase (EC 2.4.99.1) (SiaT-1) gene is localized to human chromosome 3 (q21-q28) by Southern analysis of somatic cell hybrids and by in situ hybridization of metaphase chromosomes. Comparative analysis between the human and the previously reported rat SiaT-1 genomic sequences demonstrates precise conservation of the intron/exon boundaries throughout the coding domains. Furthermore, there is extensive inter-species sequence similarity in some of the exons that contain information only for the 5'-leader regions. Human genomic sequences were also analyzed to reconcile reported differences in the 5'-untranslated region in SiaT-1 mRNAs. In cultured cell lines of the B-lineage, Reh, Nalm-6, Jok-1, Ball-1, Daudi, and Louckes, the study demonstrates that three upstream exons, Exons(Y+Z) and Exon(X), are mutually exclusively utilized, resulting in at least two distinct populations of SiaT-1 mRNA being synthesized. None of these exons is present in the SiaT-1 mRNA isotype expressed in HepG2 human hepatoma cells. In all B-lymphoblastoid cell lines examined, the basal level SiaT-1 mRNA is maintained by the expression of an isotype containing the Exons(Y+Z) sequence. The slightly smaller SiaT-1 mRNA, which contains the Exon(X) sequence but not Exons(Y+Z) sequence, is synthesized at a high level and found only in Jok-1, Daudi, and Louckes, the cell lines with mature B-cell phenotype. The study also provides further evidence that induced SiaT-1 expression accompanies the appearance of CDw75, a putatively sialylated cell surface epitope and a marker of human mature B-lymphocytes. The SiaT-1 induction is the result of the appearance of a novel form of SiaT-1 mRNA isotype.
Wang
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Department of Molecular, Roswell Park Cancer Institute, Buffalo, New York 14263.
Vertino
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Eddy
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Byers
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Jani-Sait
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Shows
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Lau
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JT
D000818:Animals; D015703:Antigens, CD / Q000235:genetics; D001402:B-Lymphocytes / Q000378:metabolism*; D001483:Base Sequence; D002478:Cells, Cultured; D002874:Chromosome Mapping; D002893:Chromosomes, Human, Pair 3; D004247:DNA; D005091:Exons; D006801:Humans; D006822:Hybrid Cells; D051379:Mice; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D012799:Sialyltransferases / Q000235:genetics*; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
D015703:Antigens, CD; D012333:RNA, Messenger; D004247:DNA; D012799:Sialyltransferases; C093493:ST6GAL1 protein, human; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase