细胞骨架调控基因Rras2的选择性多聚腺苷酸化影响细胞衰老的作用和机制

细胞衰老是组织及个体衰老的原因之一。选择性多聚腺苷酸化（APA）可决定信使RNA使用不同长度的3′非翻译区（3′UTR），并参与众多生理病理过程，但其是否在细胞衰老中起作用目前尚无报导。我们前期研究发现，小鼠和大鼠细胞衰老中APA可使3′UTR总体变长，相关基因表达量下降，并富集在细胞骨架调控等细胞衰老相关通路。其中Rras2基因长的3′UTR相比短的翻译出更少蛋白质，且敲低该基因引起了显著的细胞衰老表型。据此提出“APA可通过延长基因3′UTR调控细胞衰老”的假说。后续拟以Rras2基因为切入点，在多个细胞衰老体系中验证APA的作用，阐明APA影响细胞衰老的分子机制，确定控制长的3′UTR翻译蛋白变少的关键顺式作用元件、反式作用因子，以及衰老细胞中调控APA的上游因子，为理解细胞衰老乃至个体衰老提供新的研究角度，并为延缓衰老提供新的突破点。

Transcription is the first key step for genetics information delivery in central dogma. Transcription initiation, elongation and termination are three major steps to generate mature messenger RNA (mRNA) as template for translation. RNA processing machinery has significant functional changes in senescent cells compared to younger ones. However, the consequence of such changes remain elusive, especially regarding polyadenylation of mRNA. Alternative polyadenylation (APA) can lead to generation of distinct 3′ untranslated regions (3′ UTR) of mRNA, which affects RNA stability and localization, translation efficiency, thus plays important roles in many biological processes such as development and cancer. Our previous work showed that replicative senescent mouse cells underwent global 3′ UTR lengthening. Those genes have longer 3′ UTRs displayed decreased gene expression level and enriched in cell senescence associated pathways such as cell cytoskeleton regulation. Among them, Rras2 gene is an example. Longer 3′ UTR of Rras2 generates less protein than shorter one. Knockdown of Rras2 leads to senescence related phenotypes. We thus hypothesize that APA leads to cellular senescence via lengthening of 3′ UTR of senescence associated genes. In this proposal, we will further validate the function of APA in human cells and other types of cell senescence models. In addition, whether overexpression of Rras2 gene can reverse senescence related phenotypes will be confirmed. The mechanism under which longer 3′ UTR generates less protein will be explored. We will identify the key cis elements and trans-acting factors contributing to the protein production. Finally, which upstream factors (e.g., RNA binding proteins) control the global lengthening of 3′ UTR in senescent cells will be screened and validated. This study will deepen our understanding of cellular senescence from APA as a new angle.