Promiscuous Molecular Recognition in the C-terminal Domain of Polyadenylate Binding Protein

Blaine H. Gordon, Tianming Qu, Wei Yang, Robert Silvers.

Florida State University, Institute of Molecular Biology

Post-transcriptional control of mature eukaryotic mRNA involving the 3’ polyadenylate tail revolves around their association to cytosolic polyadenylate binding protein (PABPC1/PABP) which binds 3’ polyadenylate sequences of nearly all translatable gene products. PABP coordinates regulation by modulating mRNA circularization or recruiting protein which function to stabilize or destabilize the transcript. The C-terminal MLLE domain of PABP recognizes a single PAM2 motif of a large library of RNA regulatory protein for the pair to work in concert. This work focuses on the biophysical description of the noncanonical features of the PAM2 motif interaction with the MLLE domain comparing the PAM2 motif from LARP1 to representative PAM2 motifs from polyadenylate interaction proteins 1 and 2 (PAIP1 and PAIP2, resp.). Comparative dissections, both quantitative and qualitative, of PAM2 motif interactions with PABC through NMR spectroscopy, molecular dynamics simulations, and microscale thermophoresis elucidate features of promiscuous sequence recognition in the MLLE domain.