LARP4A recognizes polyA RNA via a novel binding mechanism mediated by disordered regions and involving the PAM2w motif, revealing interplay between PABP, LARP4A and mRNA Isabel Cruz-Gallardo Luigi Martino Geoff Kelly R Andrew Atkinson Roberta Trotta Stefano De Tito Pierre Coleman Zainab Ahdash Yifei Gu Tam TT Bui Maria R Conte 10779/crick.11357771.v1 https://crick.figshare.com/articles/journal_contribution/LARP4A_recognizes_polyA_RNA_via_a_novel_binding_mechanism_mediated_by_disordered_regions_and_involving_the_PAM2w_motif_revealing_interplay_between_PABP_LARP4A_and_mRNA/11357771 LARP4A belongs to the ancient RNA-binding protein superfamily of La-related proteins (LARPs). In humans, it acts mainly by stabilizing mRNAs, enhancing translation and controlling polyA lengths of heterologous mRNAs. These activities are known to implicate its association with mRNA, protein partners and translating ribosomes, albeit molecular details are missing. Here, we characterize the direct interaction between LARP4A, oligoA RNA and the MLLE domain of the PolyA-binding protein (PABP). Our study shows that LARP4A-oligoA association entails novel RNA recognition features involving the N-terminal region of the protein that exists in a semi-disordered state and lacks any recognizable RNA-binding motif. Against expectations, we show that the La module, the conserved RNA-binding unit across LARPs, is not the principal determinant for oligoA interaction, only contributing to binding to a limited degree. Furthermore, the variant PABP-interacting motif 2 (PAM2w) featured in the N-terminal region of LARP4A was found to be important for both RNA and PABP recognition, revealing a new role for this protein-protein binding motif. Our analysis demonstrates the mutual exclusive nature of the PAM2w-mediated interactions, thereby unveiling a tantalizing interplay between LARP4A, polyA and PABP. 2019-12-12 17:35:55 Amino Acid Motifs Autoantigens Binding Sites Cloning, Molecular Escherichia coli Gene Expression Genetic Vectors Humans Kinetics Models, Molecular Poly A Poly(A)-Binding Proteins Protein Binding Protein Conformation, alpha-Helical Protein Conformation, beta-Strand Protein Interaction Domains and Motifs RNA, Messenger RNA-Binding Proteins Recombinant Proteins Ribonucleoproteins Substrate Specificity Thermodynamics Frenkiel FC001029 NMR Developmental Biology 05 Environmental Sciences 06 Biological Sciences 08 Information and Computing Sciences