於秀麗隱桿線蟲中探討調控精子之小RNA的生成機制

Abstract

小RNA在各種物種的精子功能中起著至關重要的作用。在秀麗隱桿線蟲（Caenorhabditis elegans）中，缺乏精子相關的小RNA「alg-3/4 26G小RNA」會導致線蟲在25攝氏度時不育，然而，大多數先前的研究集中在缺乏alg-3/4 26G小RNA的病理影響上，其上游調控機制仍不清楚。因此我們的研究深入探討了26G sRNA的生物合成機制，針對類zc3h12a核糖核酸酶NYN-3如何辨識mRNA模板並進行切割進行研究。欲探討26G小RNA生成機制，我們分析了ALG-3結合的mRNA中的序列元素和轉錄起始位點（TSS），提出NYN-3的識別並不依賴特定序列，而是依靠結合轉錄起始位點的蛋白進行辨識。 根據文獻探討，我們發現線蟲中真核翻譯起始因子IFE-1作為結合轉錄起始位點的蛋白，非常有可能協助NYN-3辨認mRNA模板。IFE-1是人類真核翻譯起始因子EIF4E的直系同源物，主要表達於雄性生殖細胞系統中，並表現於雄性生殖腺的近端區域，這與NYN-3和ALG-3的基因表現相一致。我們的研究結果發現IFE-1在雄性生殖腺的近端區域與NYN-3短暫相互作用，推斷IFE-1能幫助NYN-3識別mRNA 進而產生26G sRNA合成所需的RNA模板。

Small RNAs play a crucial role in sperm function across various species. In Caenorhabditis elegans, the absence of sperm-related small RNAs, alg-3/4 26G small RNAs, results in infertility at 25 degrees Celsius. Most prior studies focused on the pathological effects of missing alg-3/4 26G small RNAs, the upstream regulatory mechanisms have remained unclear. Our research delves into the mechanisms of 26G sRNA biogenesis, particularly the targeting rules of the zc3h12a-like ribonuclease NYN-3, which is essential for the cleavage of mRNA templates required for 26G sRNA synthesis. We investigate the sequence elements and transcription start sites (TSSs) in ALG-3-bound mRNAs, proposing that NYN-3 recognition is independent of specific sequences, but rather involves interactions with TSS-binding proteins. We further identify the eukaryotic translation initiation factor IFE-1 as a potential TSS-binding protein that may assist NYN-3 in 26G sRNA biogenesis. IFE-1, an ortholog of human EIF4E, is predominantly expressed in the male germline and localizes to the proximal region of the male gonad, aligning with the expression patterns of NYN-3 and ALG-3. Our findings demonstrate that IFE-1 transiently interacts with NYN-3 at the proximal region of the male gonad, suggesting a collaborative role in recognizing target mRNAs for 26G sRNA production.