NDF/GLYR1 Promotes RNA Polymerase II Processivity via Pol II Binding and Nucleosome Destabilization

The Nucleosome Destabilizing Factor (NDF) facilitates transcription through chromatin, but its precise mechanism remains incompletely understood. Here, we identify a critical region (amino acids 140-160) within NDF that specifically interacts with phosphorylated RPB1, the largest subu-nit of elongating RNA Polymerase II (Pol II). Mutations in this region disrupt Pol II interaction and impair Pol II elongation both in vitro and in cells, yet do not affect NDF's ability to destabilize nu-cleosomes, establishing a functional separation between these two activities. Cellular studies re-veal that NDF knockout cells display faster Pol II elongation rates but produce fewer nascent tran-scripts, demonstrating NDF's primary role in maintaining transcriptional processivity through-out gene bodies. Our findings demonstrate that NDF uses distinct mechanisms to ensure productive transcription elongation rather than simply enhancing elongation speed, offering new insights in-to how transcription efficiency is maintained in chromatin. TT-seq analysis of nascent RNA and elongation speed in NDF WT and KO Hela cells, cells were treated with DRB and released for 5 and 10 min; Bru-seq analysis of nascent RNA in NDF KO SW480 cells rescued with NDF WT, MT2 or MT4.