Translational Control Of Neuronal Mrnas

Author : Mina Anadolu
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (134 download)

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Download or read book Characterizing RNA Granule-associated Stalled Polysomes written by Mina Anadolu and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Neurons have numerous mechanisms to regulate the transcription, transport and translation of mRNAs important for neurodevelopment and learning-related synaptic plasticity. When these regulatory mechanisms fail, aberrant mRNAs and dysregulated proteins can accumulate, disrupting homeostasis, and leading to the miswiring of the nervous system and intellectual disability. One example is a severe type of Autism Spectrum Disorder called Fragile X Syndrome, in which patients lack the RNA binding fragile X mental retardation protein (FMRP) that regulates the translation of many mRNAs important for synaptic function. The mechanisms of translational control that are disrupted in neurodevelopmental disorders, including Fragile X Syndrome, are not clear. Our lab has suggested that the mRNAs that are regulated by FMRP in the healthy brain, including the mRNA for the Microtubule associated protein 1b (Map1b), utilize stalled polysomes as a means of transport and regulated translation, and that this is the critical form of translational control that is disrupted during development. FMRP, as well as several other proteins associated with RNA granules are found to be enriched in a sedimentation-based purification of RNA granules from healthy post-natal rat brains. We used nucleases to digest the purified polysomes from RNA granules into monosomes and characterized the stalling profiles using Ribosome Profiling. Analysis of ribosome footprints with RNASeq revealed that polysomes recruit a large quantity of cytoskeletal mRNAs involved in neuronal development including those regulated by translation elongation through eEF2 phosphorylation. In contrast, proteins regulated by translation initiation, such as those regulated by TOR activation or through the phosphorylation of eIF4E, were not enriched. The footprints showed an enrichment for mRNAs previously predicted to be regulated by stalled polysomes, as well as many mRNAs implicated in Autism Spectrum Disorders, as identified by the Simons Foundation Autism Research Initiative (SFARI). Most importantly, we observed a significant enrichment of footprints on mRNAs previously identified by HITS-CLIP to be associated with FMRP, suggesting that a large proportion of these CLIPs were generated from RNA granule-associated mRNAs. In our footprints we saw different sized reads, which we divided into small (25 nt), medium (26-32 nt) and large (32 nt) reads. We detected an abundance of larger size ribosomal footprints with an average size of 35 nt in the RNA granules, which cluster in the coding region of mRNAs, indicating putative ribosome stalling sites. The larger footprints showed reproducible consensus peaks in the open reading frame that were enriched in purine-rich sequences, which correspond to consensus sequences for FMRP HIT-CLIPS as well as interaction motifs for m6A modifications. The evidence supports the stalling of elongating ribosomes on specific mRNA sequences. These sequences may be directly targeted by FMRP and other RBPs that are implicated in the regulation of stalled mRNAs and their recruitment to RNA Granules for transport. Alternatively, these sequences may stall elongating ribosomes through an independent mechanism, and techniques such as CLIP identify these sequences as consensus sequences for RBPs because the RBPs associate with the ribosomes that are stalled on these sequences"--