Identification of SAP155 as the Target of GEX1A (Herboxidiene), an Antitumor Natural Product
Identification of SAP155 as the Target of GEX1A (Herboxidiene), an Antitumor Natural Product
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DOI：
10.1021/cb100248e
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发表时间：
2011-03-01
影响因子：
4
通讯作者：
Mizukami, Tamio
中科院分区：
文献类型：
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作者：
Hasegawa, Makoto;Miura, Tatsuhiro;Mizukami, Tamio
GEX1A是一种具有抗肿瘤活性的微生物产品。用GEX1A培养的HeLa细胞累积p27(Kip)及其C端截短形式p27*。GEX1A抑制p27的前mRNA剪接，从含有第一内含子的未剪接的mRNA中产生p27*。P27*缺乏E3连接酶介导的p27蛋白降解所需的位点，导致其在GEX1A处理的细胞中积聚。积累的p27*能够结合并抑制细胞周期蛋白E-CDK2复合体，该复合体导致E3连接酶介导的p27降解，从而可能触发p27的积累。通过使用一系列GEX1A光亲和标记衍生物，我们发现GEX1A靶向SAP155蛋白，SAP155蛋白是SF3B的一个亚基，负责前mRNA剪接。GEX1A药效团和光反应基团之间的连接子长度对于检测GEX1A结合蛋白至关重要。GEX1A是一种新型的剪接抑制因子，通过与SAP155结合，特异性地削弱SF3B的功能。
GEX1A is a microbial product with antitumor activity. HeLa cells cultured with GEX1A accumulated p27(Kip) and its C-terminally truncated form p27*. GEX1A inhibited the pre-mRNA splicing of p27, producing p27* from the unspliced mRNA containing the first intron. p27* lacked the site required for E3 ligase-mediated proteolysis of p27, leading to its accumulation in GEX1A-treated cells. The accumulated p27* was able to bind to and inhibit the cyclin E-Cdk2, complex that causes E3 ligase-mediated degradation of p27, which probably triggers, the accumulation of p27. By using a series of photoaffinity-labeling derivatives of GEX1A, we found that GEX1A targeted SAP155 protein, a subunit of SF3b responsible for pre-mRNA splicing. The linker length between the GEX1A pharmacophore and the photoreactive group was critical for detection of the GEX1A-binding protein. GEX1A serves as novel splicing inhibitor that specifically impairs the SF3b function by binding to SAP155.