Identification of Cpeb4 binders in cardiomyocyte

Mutations or decreased expression of RNA-binding proteins (mRBPs) can lead to cardiomyopathies in humans. Here we defined RBPs in healthy and diseased primary cardiomyocytes at a system-wide level by RNA Interactome Capture. This identified 67 novel cardiomyocyte specific RBPs including several contractile proteins. Furthermore, we identified Cytoplasmic polyadenylation element binding protein 4 (Cpeb4) as a dynamic mRBP in diseased cardiomyocytes, regulating cardiac growth both in vitro and in vivo. To study Cpeb4 in cardiomyocytes, we identified mRNAs bound to and regulated by Cpeb4. Cpeb4 regulates cardiac remodeling by differential expression of transcription factors. Among Cpeb4 target mRNAs, two Zinc finger transcription factors (Zeb1 and Zbtb20) were identified. We show that Cpeb4 regulates the translation of these mRNAs and that Cpeb4 depletion increases their expression. Thus, Cpeb4 emerges as critical regulator of cardiomyocyte function by differential binding of specific mRNAs in response to pathological growth stimulation.RNA结合蛋白（RNA-binding proteins, RBPs）的突变或表达下调可诱发人类心肌病。本研究采用RNA互作组捕获（RNA Interactome Capture）技术，在全系统层面解析了健康与患病原代心肌细胞中的RBPs表达谱，共鉴定出67个新型心肌细胞特异性RBPs，其中包含多种收缩蛋白。进一步研究发现，胞质多聚腺苷酸化元件结合蛋白4（Cytoplasmic polyadenylation element binding protein 4, Cpeb4）是患病心肌细胞中的动态功能异常RBPs，可在体外与体内调控心脏生长。为探究Cpeb4在心肌细胞中的调控作用，我们鉴定了其结合并调控的信使RNA（messenger RNA, mRNA）。Cpeb4通过调控转录因子的差异表达参与心肌重构。在Cpeb4的靶mRNA中，我们鉴定出两个锌指转录因子（Zeb1与Zbtb20）。实验结果证实，Cpeb4可调控这两种mRNA的翻译过程，且Cpeb4敲低会提升其靶mRNA的表达水平。综上，Cpeb4可通过在病理生长刺激下特异性结合不同mRNA，成为心肌细胞功能的关键调控因子。