(2011) Alternative splicing variants of human arsenic (+3oxidation state) methyltransferase.
(2011) Alternative splicing variants of human arsenic (+3oxidation state) methyltransferase.
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(2011) 人砷（三氧化态）甲基转移酶的选择性剪接变体。
DOI：
10.1016/j.bbrc.2011.10.008
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
S.
中科院分区：
文献类型：
--
作者：
Sumi;D.;Fukushima;K.;Miyataka;H.;Himeno;S.
砷(+3氧化态)甲基转移酶(AS3MT)催化三价砷(As(III))甲基化生成一甲基砷酸(MMA(V))和二甲基砷酸(DMA(V))，在砷化合物的解毒过程中起着重要作用。在这里，我们报告了人类AS3MT基因的两个剪接变异体的鉴定。另一个是外显子4和外显子5的剪接变异体(Δ4，5)，产生31.1 kDa的AS3MT蛋白。除AS3MT的全长基因外，Δ-4、5mRNAs在肝癌细胞株、A549细胞、HL60细胞、K562细胞和HEK293细胞中均有表达。对从大肠杆菌中纯化的重组Δ4，5AS3MT和野生型AS3MT蛋白的甲基转移酶活性进行了测定。高效液相-电感耦合等离子体质谱分析表明，As(Ⅲ)与野生型As3MT蛋白孵育后出现明显的MMA(V)峰，而与Δ4，5As3MT蛋白孵育后未见明显的MMA(V)峰。此外，转染Δ4，5AS3MT基因的COS7细胞不能将AS(III)转化为MMA(V)或DMA(V)。Δ-4，5AS3MT甲基转移酶活性的缺乏可能与S-腺苷蛋氨酸结合位点和关键的半胱氨酸残基的缺失有关。这些数据表明，AS3MT基因剪接变异体的表达模式可能影响细胞中砷甲基化的能力。
Arsenic (+3 oxidation state) methyltransferase (As3MT) catalyzes the methylation of trivalent arsenic (As(III)) to monomethylarsonate (MMA(V)) and dimethylarsinic acid (DMA(V)), and plays an important role in the detoxification of arsenicals. Here, we report the identification of two splicing variants of the human As3MT gene. One splicing variant was an exon-3 skipping (Δ3) form which produced a premature stop codon, and the other was an exon-4 and -5 skipping (Δ4,5) form which produced a 31.1kDa As3MT protein. In addition to the full-length mRNA of As3MT, Δ4,5 mRNAs were detected in HepG2, A549, HL60, K562, and HEK293 cells. The methyltransferase activity of the recombinant Δ4,5 As3MT and wild-type As3MT proteins purified from Escherichia coli was determined. Speciation analysis by HPLC–ICP-MS showed a clear peak of MMA(V) after incubation of As(III) with the wild-type As3MT protein, but not with the Δ4,5 As3MT protein. In addition, COS-7 cells transfected with Δ4,5 As3MT cDNA did not convert As(III) to MMA(V) or DMA(V). The lack of methyltransferase activity of Δ4,5 As3MT seems to be related to the deletion of an S-adenosylmethionine-binding site and a critical cysteine residue. These data suggest that the expression pattern of splicing variants of the As3MT gene may affect the capacity for arsenic methylation in cells.