Crosstalk between CPEB1 and miR-135 family members

MicroRNAs (miRNAs) are master regulators of gene expression at the post-transcriptional level, controlling sets of genes and entire biological pathways. Neuronal miRNAs have emerged as key modulators of synaptic function and plasticity. We recently showed that the neuronal miR-135a regulates neuronal activity and plasticity mechanisms, as well as complex behaviors such as stress and anxiety. miR-135a belongs to the mir-135 family including two isoforms, miR-135a and miR-135b, with the first being encoded by two genes. RNA-Binding Proteins (RBPs) play a crucial role in determining miRNA function, as they control various stages of miRNA biogenesis, localization, degradation, and activity. The interplay between RBPs and miRNAs is essential for fine-tuning of gene expression in neurons, particularly during dynamic processes like synaptic plasticity. In this study, we investigate the interaction between the RBP Cytoplasmic Polyadenylation Element Binding Protein 1 (CPEB1) and members of the miR-135 family, analyzing their binding features and functional implications. CPEB1 recognizes a 5-6 nucleotide long U-rich sequence present in the target RNA, known as the cytoplasmic polyadenylation element (CPE). Both miR-135a and miR-135b contain a CPE motif within their nucleotide sequences. By in vitro studies, we demonstrate the high-affinity binding of pre-miR-135A1, pre-miR-135A2, and pre-miR-135B human miR-135 precursors to the RNA Recognition Motifs (RRM1-RRM2) of CPEB1. By RNA immunoprecipitation (RIP) experiments on HEK293 human cells we demonstrate that miR-135 precursors bind to the CPEB1 protein. To assess the role of CPEB1 in miR-135 biogenesis, we performed functional assays on mammalian neuronal cells. By knockdown and overexpression experiments we demonstrate that CPEB1 impacts miRNA biogenesis. The mechanisms involved and the functional consequences will be discussed.