OCT4 interprets and enhances nucleosome flexibility

Abstract

Pioneer transcription factors induce cellular identity transitions by binding to sites on inaccessible DNA wrapped in nuclear chromatin. They contribute to chromatin opening and recruit other factors to regulatory DNA sites. The structural basis of their interaction with the chromatin structural unit, the nucleosome, is still unresolved. From a combination of experiments and molecular simulations we reveal here how Oct4, the master regulator and inducer of cellular pluripotency, interprets and enhances nucleosome structural flexibility. The magnitude of Oct4 impact on nucleosome dynamics depends on the binding site position and the mobility of unstructured tails of nucleosomal histone proteins. Oct4 propagates and stabilizes open nucleosome conformations by specific sequence recognition and unspecific DNA exploration. Our findings provide a structural basis for the versatility of transcription factors in engaging with nucleosomes and have implications for understanding how pioneer factors induce chromatin dynamics.