Conformational Dynamics of hAgo2 Silencing: Decoding Functional Divergence across Human Argonaute Paralogs

RNA interference (RNAi) is a key mechanism for controlling gene expression, with Argonaute (Ago) proteins serving as core effectors of the RNA-induced silencing complex (RISC). By loading small noncoding RNAs, Agos target complementary messanger RNAs (mRNAs), leading to their direct catalytic cleavage or the activation of translational repression. Among the four human Ago isoforms (hAgo1-4), only hAgo2 exhibits catalytic activity, a feature not fully explained by structural differences alone. This study explores the structural and functional distinctions among hAgo isoforms, both in their unbound and bound states, using miRNA-20a as a model system. Microsecond-scale molecular dynamics (MD) simulations reveal insightful differences in structural flexibility and plasticity. Catalytically active hAgo2 demonstrates enhanced conformational dynamics, enabling essential structural transitions for efficient RNA silencing. Conversely, hAgo4 exhibits a more rigid conformation, consistent with its reduced catalytic activity. These findings suggest that human isoforms employ a conformational selection mechanism, where the interplay between structural rigidity and flexibility fine-tunes their functional roles. The isoform-specific dynamics unveiled in this study illuminate the functional specialization of human Ago isoforms, providing critical insights into their distinct role in RNA silencing. This understanding opens new possibilities for therapeutic innovation by modulating Ago-mediated pathways in an isoform-specific manner.