Kim K W, Kim S W, Min K S, Kim C H, Lee Y C
Division of Biotechnology, Faculty of Natural Resources and Life Science, Dong-A University, 604-714, Busan, South Korea.
Gene. 2001 Aug 8;273(2):163-71. doi: 10.1016/s0378-1119(01)00595-9.
GM3 synthase, which transfers CMP-NeuAc with an alpha2,3-linkage to a galactose residue of lactosylceramide, plays a key role in the biosynthesis of all complex gangliosides. In this study, cDNA and genomic clones encoding human GM3 synthase (hST3Gal V) were isolated, and the structural organization of the gene was determined. The hST3Gal V cDNA was identical in the coding region with cDNA that has been cloned previously from the HL-60 cells but different in the 5'-untranslated region (UTR). The hST3Gal V gene consisted of nine exons, which span approximately 44 kb, with exons ranging in size from 112 to 1242 bp. The coding region was located in exons 4-9, and all exon-intron boundaries except the acceptor site of intron 1 followed the GT-AG rule. The expression of this gene was highly restricted in both human fetal and adult tissues. By comparison of the nucleotide sequences of the genomic DNA with cDNA sequences including 5'-RACE products, we identified four isoforms (types 1-4) of the hST3Gal V mRNA that differ only in the 5'-UTR. Structural analysis of these isoforms suggests that mRNA isoforms of hST3Gal V are produced by a combination of alternative splicing and alternative promoter utilization.
GM3合酶可将具有α2,3连接的CMP-唾液酸转移至乳糖基神经酰胺的半乳糖残基上，在所有复合神经节苷脂的生物合成中起关键作用。在本研究中，分离出了编码人GM3合酶（hST3Gal V）的cDNA和基因组克隆，并确定了该基因的结构组织。hST3Gal V cDNA的编码区与先前从HL-60细胞中克隆的cDNA相同，但5'-非翻译区（UTR）不同。hST3Gal V基因由9个外显子组成，跨度约为44 kb，外显子大小从112到1242 bp不等。编码区位于外显子4-9中，除内含子1的受体位点外，所有外显子-内含子边界均遵循GT-AG规则。该基因的表达在人类胎儿和成人组织中均受到高度限制。通过比较基因组DNA的核苷酸序列与包括5'-RACE产物在内的cDNA序列，我们鉴定出了hST3Gal V mRNA的四种异构体（1-4型），它们仅在5'-UTR上有所不同。对这些异构体的结构分析表明，hST3Gal V的mRNA异构体是由选择性剪接和选择性启动子利用共同产生的。
