生物物理所Cell Res揭示疾病蛋白在DNA损伤修复中的作用机理

中科院生物物理所，美国MD安德森癌症中心等处的研究人员报道了FAAP24（Fanconi anemia associated protein 24KD）的三维结构，通过结构分析对其在DNA损伤修复中ssDNA结合活性以及结构域功能进行了体内体外的实验验证。

　　

2013年9月3日，《Cell Research》杂志在线发表了题为“Structure analysis of FAAP24 reveals single-stranded DNA-binding activity and domain functions in DNA damage response”的论文，报道了FAAP24（Fanconi anemia associated protein 24KD）的三维结构，通过结构分析对其在DNA损伤修复中ssDNA结合活性以及结构域功能进行了体内体外的实验验证。

这项研究由中科院生物物理所龚为民课题组、合肥强磁场中心田长麟课题组以及美国MD安德森癌症中心Lei Li课题组合作完成。

范可尼贫血（Fanconi anemia ，FA）是由基因变异引发的常染色体隐形遗传病，FA 基因突变会导致骨髓障碍，癌症，早衰等一系列疾病。目前已经找到了与范科尼贫血相关的15个基因，其中FANCM–FAAP24异二聚体复合物能够感知DNA损伤，募集通路中其它成员至损伤DNA处启动下游的修复工作。

这项研究在通过NMR手段解析了FAAP24溶液结构，结合序列分析和结构比对，找到了参与ssDNA结合的关键氨基酸残基G168, G170, K171 and K173，设计了一系列突变体通过体外SPR，NMR滴定实验对此进行验证，并通过体内实验进一步确定与染色质结合的氨基酸位点的正确性。通过截短体实验确定FAAP24-(HhH)2结构域对ssDNA以及FANCM的结合的关键性作用。

该研究揭示了FAAP24在DNA损伤修复中的双重功能，进一步阐明了FA蛋白参与DNA损伤修复的分子机制。

原文摘要：

Structure analysis of FAAP24 reveals single-stranded DNA-binding activity and domain functions in DNA damage response

The FANCM/FAAP24 heterodimer has distinct functions in protecting cells from complex DNA lesions such as interstrand crosslinks. These functions rely on the biochemical activity of FANCM/FAAP24 to recognize and bind to damaged DNA or stalled replication forks. However, the DNA-binding activity of this complex was not clearly defined. We investigated how FAAP24 contributes to the DNA-interacting functions of the FANCM/FAAP24 complex by acquiring the N-terminal and C-terminal solution structures of human FAAP24. Modeling of the FAAP24 structure indicates that FAAP24 may possess a high affinity toward single-stranded DNA (ssDNA). Testing of various FAAP24 mutations in vitro and in vivo validated this prediction derived from structural analyses. We found that the DNA-binding and FANCM-interacting functions of FAAP24, although both require the C-terminal (HhH)2 domain, can be distinguished by segregation-of-function mutations. These results demonstrate dual roles of FAAP24 in DNA damage response against crosslinking lesions, one through the formation of FANCM/FAAP24 heterodimer and the other via its ssDNA-binding activity required in optimized checkpoint activation.