Complex interplay between FMRP and DHX9 during DNA replication stress.
Complex interplay between FMRP and DHX9 during DNA replication stress.
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DOI：
10.1016/j.jbc.2023.105572
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发表时间：
2024-01
影响因子：
4.8
通讯作者：
Feng, Wenyi
中科院分区：
文献类型：
--
作者：
Chakraborty, Arijita;Dutta, Arijit;Dettori, Leonardo G;Daoud, Rosemarie;Li, Jing;Gonzalez, Leticia;Xue, Xiaoyu;Hehnly, Heidi;Sung, Patrick;Bah, Alaji;Feng, Wenyi
脆性X信使核糖核蛋白（FMRP）的突变或缺陷导致脆性X综合征（FXS），这是遗传性智力残疾的最常见原因。FMRP是一种核质蛋白，主要特征为翻译阻遏物，其核功能知之甚少。我们最近报道，缺乏FMRP的FXS患者细胞比正常细胞维持更高水平的DNA双链断裂（DSB），特别是在易于形成R环的序列处，这是一种因DNA复制应激而进一步加剧的表型。此外，FMRP的表达，而不是已知引起FXS的FMRPI 304 N突变体的表达，减少了R环相关的DSB。我们随后报道，重组FMRP直接结合R-环，主要是通过羧基末端的固有无序区。在这里，我们表明FMRP直接与RNA解旋酶DHX 9相互作用。这种相互作用由FMRP的氨基末端结构域介导，用FMRPI 304 N降低。我们还表明，FMRP抑制DHX 9解旋酶活性的RNA：DNA杂交体和抑制也依赖于氨基末端。此外，FMRPI 304 N突变导致FMRP和DHX 9在复制应激中持续存在于染色质上。这些结果表明FMRP和DHX 9在染色质处的拮抗关系，其中它们的适当相互作用导致两种蛋白质从完全解析的R环解离。我们提出，FMRP功能的缺失或丧失分别导致DHX 9或两种蛋白质在未解析的R环上持续存在，最终导致DSB。我们的研究为我们理解FMRP的基因组功能提供了新的思路。
Mutations in, or deficiency of, fragile X messenger ribonucleoprotein (FMRP) is responsible for the Fragile X syndrome (FXS), the most common cause for inherited intellectual disability. FMRP is a nucleocytoplasmic protein, primarily characterized as a translation repressor with poorly understood nuclear function(s). We recently reported that FXS patient cells lacking FMRP sustain higher level of DNA double-strand breaks (DSBs) than normal cells, specifically at sequences prone to forming R-loops, a phenotype further exacerbated by DNA replication stress. Moreover, expression of FMRP, and not an FMRPI304N mutant known to cause FXS, reduced R-loop-associated DSBs. We subsequently reported that recombinant FMRP directly binds R-loops, primarily through the carboxyl terminal intrinsically disordered region. Here, we show that FMRP directly interacts with an RNA helicase, DHX9. This interaction, which is mediated by the amino terminal structured domain of FMRP, is reduced with FMRPI304N. We also show that FMRP inhibits DHX9 helicase activity on RNA:DNA hybrids and the inhibition is also dependent on the amino terminus. Furthermore, the FMRPI304N mutation causes both FMRP and DHX9 to persist on the chromatin in replication stress. These results suggest an antagonistic relationship between FMRP and DHX9 at the chromatin, where their proper interaction leads to dissociation of both proteins from the fully resolved R-loop. We propose that the absence or the loss of function of FMRP leads to persistent presence of DHX9 or both proteins, respectively, on the unresolved R-loop, ultimately leading to DSBs. Our study sheds new light on our understanding of the genome functions of FMRP.