Transcribed CGG repeat expansions cause neurodegeneration in Fragile X-associated tremor/ataxia syndrome (FXTAS). CGG repeat RNAs sequester RNA-binding proteins (RBPs) into nuclear foci and undergo repeat-associated non-AUG (RAN) translation into toxic peptides. To identify proteins involved in these processes, we employed a CGG repeat RNA-tagging system to capture repeat-associated RBPs by mass spectrometry in mammalian cells. We identified several SR (serine/arginine-rich) proteins that interact selectively with CGG repeats basally and under cellular stress. These proteins modify toxicity in a Drosophila model of FXTAS. Pharmacologic inhibition of serine/arginine protein kinases (SRPKs), which alter SRSF protein phosphorylation, localization, and activity, directly inhibits RAN translation of CGG and GGGGCC repeats (associated with C9orf72 ALS/FTD) and triggers repeat RNA retention in the nucleus. Lowering SRPK expression suppressed toxicity in both FXTAS and C9orf72 ALS/FTD model flies, and SRPK inhibitors suppressed CGG repeat toxicity in rodent neurons. Together, these findings demonstrate roles for CGG repeat RNA binding proteins in RAN translation and repeat toxicity and support further evaluation of SRPK inhibitors in modulating RAN translation associated with repeat expansion disorders.

中文翻译：

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SRSF 蛋白激酶 1 调节 RAN 翻译并抑制 CGG 重复毒性

转录的 CGG 重复扩增会导致脆性 X 相关震颤/共济失调综合征 (FXTAS) 的神经变性。CGG 重复 RNA 将 RNA 结合蛋白 (RBP) 隔离到核灶中，并进行重复相关的非 AUG (RAN) 翻译成有毒肽。为了鉴定参与这些过程的蛋白质，我们采用 CGG 重复 RNA 标记系统，通过质谱法在哺乳动物细胞中捕获重复相关的 RBP。我们鉴定了几种 SR（富含丝氨酸/精氨酸）蛋白，它们在基底和细胞应激下选择性地与 CGG 重复序列相互作用。这些蛋白质改变了FXTAS果蝇模型中的毒性。丝氨酸/精氨酸蛋白激酶 (SRPK) 的药理学抑制可改变 SRSF 蛋白磷酸化、定位和活性，直接抑制 CGG 和 GGGGCC 重复序列（与 C9orf72 ALS/FTD 相关）的 RAN 翻译，并触发重复 RNA 在细胞核中保留。降低 SRPK 表达可抑制 FXTAS 和 C9orf72 ALS/FTD 模型果蝇的毒性，SRPK 抑制剂可抑制啮齿动物神经元中的 CGG 重复毒性。总之，这些发现证明了 CGG 重复 RNA 结合蛋白在 RAN 翻译和重复毒性中的作用，并支持进一步评估 SRPK 抑制剂在调节与重复扩展障碍相关的 RAN 翻译方面的作用。