The Nucleosomal Binding Proteins HMGN Stabilize Cell Identity. Mus musculus strain:C57BL/6

The dynamic nature of the chromatin epigenetic landscape plays a key role in the establishment and maintenance of cell identity, yet the factors that affect the dynamics of the epigenome are not fully known. We find that the ubiquitous nucleosome binding proteins HMGN1 and HMGN2, preferentially colocalize with epigenetic marks of active chromatin, and with cell-type specific enhancers. Loss of HMGNs enhances the rate of OSKM induced reprograming of mouse embryonic fibroblasts (MEFs) into pluripotent embryonic stem cells (ESCs), and the ASHL1 induced direct conversion of fibroblast into neurons. During transcription factor induced reprogramming to pluripotency, loss of HMGNs accelerates the erasure of the MEF-specific epigenetic landscape and the establishment of an ESCs-specific chromatin landscape, without affecting the pluripotency potential of the reprogrammed cells. Thus, HMGN proteins affect the plasticity of the chromatin epigenetic landscape thereby stabilizing, rather than determining cell identity