A SWI/SNF subunit regulates chromosomal dissociation of structural maintenance complex 5 during DNA repair in plant cells
A SWI/SNF subunit regulates chromosomal dissociation of structural maintenance complex 5 during DNA repair in plant cells
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SWI/SNF 亚基在植物细胞 DNA 修复过程中调节结构维持复合物 5 的染色体解离
DOI：
10.1073/pnas.1900308116
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发表时间：
2019-07-23
影响因子：
11.1
通讯作者：
Yang, Chengwei
中科院分区：
文献类型：
--
作者：
Jiang, Jieming;Mao, Ning;Yang, Chengwei
意义DNA修复对于在所有类型的细胞中准确地维持遗传信息是必不可少的，但在这一过程中涉及的复合体的调节机制尚不清楚。结构维持复合体5/6(SMC5/6)在正常情况下与染色体结合，并被招募到DNA双链断裂进行修复。然而，在DNA修复过程中，这种保守的复合体从其原始染色体位置解离的机制完全未知。在这里，我们描述了一种机制，其中SMC5在植物细胞中的染色体解离是通过SWI/SNF复合体的一个亚基SWI3B介导的。鉴于这些蛋白质在进化上是保守的，目前的发现可能会为其他物种的DNA修复研究提供线索。DNA损伤降低了基因组的稳定性，并改变了所有生物体的遗传信息。在真核生物中进化出了用于DNA修复的保守蛋白质复合体，如结构维护复合体5/6(SMC5/6)，它是一种参与DNA双链断裂(DSB)修复的染色体ATPase。SMC5/6向DSB募集的因素已被确定，但这种复合体在正常情况下也与染色体有关；SMC5/6如何从其原始位置解离并转移到DSB位置完全未知。在本研究中，我们确定SWI3B是SWI/SNF复合体的一个亚基，是拟南芥中SMC5相互作用的蛋白。敲除SWI3B或SMC5会导致DNA损伤积累增加。在DNA损伤过程中，SWI3B被诱导表达，但SWI3B蛋白不定位于DSB。值得注意的是，SWI3B的下调或过表达都会扰乱SMC5的DSB招募，以应对DNA损伤。共转录激活子ADA2b的过表达显著地挽救了SMC5在SWI3B过表达细胞中的DSB定位，但在SWI3B基因敲除细胞中的定位很弱。生化数据证实，ADA2b减弱了SWI3B和SMC5之间的相互作用，而SWI3B促进了SMC5从染色体上解离。此外，SMC5的过表达减少了SWI3B基因敲除植物的DNA损伤积累。综上所述，这些结果表明，适当水平的SWI3B的存在促进了SMC5从染色体上的解离，以便在植物细胞DNA损伤时进一步在DSB处重新募集。
Significance DNA repair is essential for accurate maintenance of genetic information in all types of cells, but what regulatory mechanisms act on the complexes involved in this process has been unclear. The structural maintenance complex 5/6 (SMC5/6) associates with chromosomes under normal conditions and is recruited to DNA double-strand breaks for repair. However, the mechanism by which this conserved complex becomes dissociated from its original chromosomal location during DNA repair is completely unknown. Here, we describe a mechanism in which the chromosomal dissociation of SMC5 in plant cells is mediated via SWI3B, a subunit of the SWI/SNF complex. Given that these proteins are evolutionarily conserved, the current findings may provide hints for the study of DNA repair in other species. DNA damage decreases genome stability and alters genetic information in all organisms. Conserved protein complexes have been evolved for DNA repair in eukaryotes, such as the structural maintenance complex 5/6 (SMC5/6), a chromosomal ATPase involved in DNA double-strand break (DSB) repair. Several factors have been identified for recruitment of SMC5/6 to DSBs, but this complex is also associated with chromosomes under normal conditions; how SMC5/6 dissociates from its original location and moves to DSB sites is completely unknown. In this study, we determined that SWI3B, a subunit of the SWI/SNF complex, is an SMC5-interacting protein in Arabidopsis thialiana. Knockdown of SWI3B or SMC5 results in increased DNA damage accumulation. During DNA damage, SWI3B expression is induced, but the SWI3B protein is not localized at DSBs. Notably, either knockdown or overexpression of SWI3B disrupts the DSB recruitment of SMC5 in response to DNA damage. Overexpression of a cotranscriptional activator ADA2b rescues the DSB localization of SMC5 dramatically in the SWI3B-overexpressing cells but only weakly in the SWI3B knockdown cells. Biochemical data confirmed that ADA2b attenuates the interaction between SWI3B and SMC5 and that SWI3B promotes the dissociation of SMC5 from chromosomes. In addition, overexpression of SMC5 reduces DNA damage accumulation in the SWI3B knockdown plants. Collectively, these results indicate that the presence of an appropriate level of SWI3B enhances dissociation of SMC5 from chromosomes for its further recruitment at DSBs during DNA damage in plant cells.