Human hnRNPA1 reorganizes telomere-bound Replication Protein A

Abstract

AbstractHuman replication protein A (RPA) is a heterotrimeric ssDNA binding protein responsible for many aspects of cellular DNA metabolism. The binding and dissociation of the four individual DNA binding domains (DBDs) from DNA result in configurational dynamics of the RPA-DNA complexes. This dynamics is essential for replacement of RPA by downstream proteins in various cellular metabolic pathways. RPA plays several important functions at telomeres where it binds to and melts telomeric G-quadruplexes, non-canonical DNA structures formed at the G-rich telomeric ssDNA overhangs. Here, we combine single-molecule total internal reflection fluorescence microscopy (smTIRFM) and mass photometry (MP) with biophysical and biochemical analyses to demonstrate that heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) specifically remodels RPA bound to telomeric ssDNA by dampening the RPA configurational dynamics and forming a stable ternary complex. Uniquely, among hnRNPA1 target RNAs, telomeric repeat-containing RNA (TERRA) is selectively capable of releasing hnRNPA1 from the RPA-telomeric DNA complex. We speculate that this telomere specific RPA-DNA-hnRNPA1 complex is an important structure in telomere protection.One Sentence SummaryAt the single-stranded ends of human telomeres, the heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) binds to and modulates conformational dynamics of the ssDNA binding protein RPA forming a ternary complex which is controlled by telomeric repeat-containing RNA (TERRA).