Grahn Ammi, Barkhordar Giti Shah, Larson Göran
Institute of Laboratory Medicine, Department of Clinical Chemistry and Transfusion Medicine, Sahlgrenska University Hospital, SE 413 45 Göteborg, Sweden.
Glycoconj J. 2004;20(7-8):493-500. doi: 10.1023/B:GLYC.0000038295.87747.0b.
We have recently cloned and sequenced 19 human ST3Gal III gene isotranscripts from peripheral blood leukocytes and identified very complex patterns of isotranscripts of this gene in neuronal tissues. We have now cloned and sequenced additionally seven new isotranscripts from foetal brain. These novel isotranscripts showed losses of complete exons along the whole length of the coding sequence. None of the new isotranscripts coded for proteins with the two (L- and S-) sialylmotifs intact. One of the isotranscripts belonged to the isoform ST3Gal III -B, five to the ST3Gal III -C isoform and one to ST3Gal III -D isoform of isotranscripts, which lacks exon 3, exons 3 and 4 and exon 4 respectively. Two of the C series isotranscripts, ST3Gal III C4 and C11 had both lost exons 12 and 13 containing the S-motif but had otherwise the L- and the VS-motifs intact. Three isotranscripts, ST3Gal III C5, C12 and D5, were similar in the 3'-end coding for an identical amino acid sequence unrelated to the original enzyme. Isotranscripts ST3Gal III C9 and B10 were distinctly different from all other forms identified so far. The splice variants reported here are unlikely to express enzymatic activities but may other biological functions.
我们最近从外周血白细胞中克隆并测序了19种人类ST3Gal III基因的同工转录本，并在神经组织中鉴定出该基因同工转录本的非常复杂的模式。我们现在又从胎儿脑中克隆并测序了7种新的同工转录本。这些新的同工转录本在整个编码序列中都出现了完整外显子的缺失。没有一个新的同工转录本编码的蛋白质具有完整的两个（L-和S-）唾液酸基序。其中一个同工转录本属于同工型ST3Gal III -B，五个属于ST3Gal III -C同工型，一个属于ST3Gal III -D同工型，它们分别缺失外显子3、外显子3和4以及外显子4。C系列的两个同工转录本，ST3Gal III C4和C11都缺失了包含S-基序的外显子12和13，但L-和VS-基序在其他方面是完整的。三个同工转录本，ST3Gal III C5、C12和D5，在3'-末端编码相同的氨基酸序列，与原始酶无关。同工转录本ST3Gal III C9和B10与迄今为止鉴定出的所有其他形式明显不同。这里报道的剪接变体不太可能表达酶活性，但可能具有其他生物学功能。
