生物合成过程图
结构复杂的天然产物历来是抗肿瘤药物的重要来源。FR901464是假单孢菌产生的、结构独特且具有全新作用机制（作用于mRNA剪接体系的SF3b复合物）的高活性抗肿瘤天然产物（对多种人癌细胞体外的IC50为0.6-3.4 nM），近年来引起了有机合成、药物化学及化学生物学等多方面的关注。
中科院上海有机化学研究所生命有机化学国家重点实验室的科研人员经过三年多的努力，采用PCR克隆特异的羟基-甲基戊二酰辅酶A合成酶(HCS)基因的方法，从假单孢菌sp. No. 2663中克隆了完整的FR901464生物合成基因簇。该基因簇包含20个基因，编码5个“AT-less”聚酮合成酶(PKS)，1个杂合的聚酮/非核糖体聚肽合成酶(PKS/NRPS)，1个非核糖体聚肽合成酶(NRPS)，3个独立的酰基转移酶(AT)，4个聚酮骨架β-烷基化相关蛋白，4个后修饰酶，2个调控蛋白。
通过体内基因敲除和体外生化实验相结合，研究人员初步阐明了FR901464独特的生物合成途径：采用高度杂合的“AT-less”PKS-NRPS-HCS三元体系，以甘油作为PKS的起始单元、Baeyer-Villiger氧化解离聚酮链。
该研究揭示了自然界聚酮天然产物生物合成中复杂多样的生物合成机理，为进一步发现新的酶催化反应并通过对其生物合成基因的调控产生结构类似物创造了条件。
该研究工作得到国家自然科学基金委、科技部、中国科学院和上海市科委的资助，部分研究结果发表于J. Am. Chem. Soc. （2011, 133, 2452-2462）。（生物谷Bioon.com）
生物谷推荐原文出处：
J. Am. Chem. Soc., 2011, 133 (8), pp 2452–2462 DOI: 10.1021/ja105649g
Cloning and Elucidation of the FR901464 Gene Cluster Revealing a Complex Acyltransferase-less Polyketide Synthase Using Glycerate as Starter Units
Feng Zhang, Hai-Yan He, Man-Cheng Tang, Yu-Min Tang, Qiang Zhou, and Gong-Li Tang*
FR901464, an antitumor natural product, represents a new class of potent anticancer small molecules targeting spliceosome and inhibiting both splicing and nuclear retention of pre-mRNA. Herein we describe the biosynthetic gene cluster of FR901464, identified by degenerate primer PCR amplification of a gene encoding the 3-hydroxy-3-methylglutaryl-CoA synthase (HCS) postulated to be involved in the biosynthesis of a β-branched polyketide from Pseudomonas sp. No. 2663. This cluster consists of twenty open reading frames (ORFs) and was localized to 93-kb DNA segment, and its involvement in FR901464 biosynthesis was confirmed by gene inactivation and complementation. FR901464 is biosynthesized by a hybrid polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS), HCS, and acyltransferases (AT)-less system. The PKS/NRPS modules feature unusual domain organization including multiple domain redundancy, inactivation, and tandem. Biochemical characterization of a glyceryl transferase and an acyl carrier protein (ACP) in the start module revealed that it incorporates D-1,3-bisphosphoglycerate, which is dephosphorylated and transferred to ACP as the starter unit. Furthermore, an oxidative Baeyer?Villiger reaction followed by chain release was postulated to form a pyran moiety. On the basis of in silico analysis and genetic and biochemical evidances, a biosynthetic pathway for FR901464 was proposed, which sets the stage to further investigate the complex PKS biochemically and engineer the biosynthetic machinery for the production of novel analogues.