Binds to the inner side of the nucleosomal DNA thus altering the interaction between the DNA and the histone octamer. May be involved in the process which maintains transcribable genes in a unique chromatin conformation. Inhibits the phosphorylation of nucleosomal histones H3 and H2A by RPS6KA5/MSK1 and RPS6KA3/RSK2 (By similarity). Interacts with transcriptional regulator SEHBP. Cytoplasmic enrichment upon phosphorylation. The RNA edited version localizes to the nucleus. Phosphorylation on Ser-21 and Ser-25 weakens binding to nucleosomes and increases the rate of H3 phosphorylation (By similarity). Phosphorylation favors cytoplasmic localization. Partially edited. A new initiator methionine may be created by a single uridine insertion in the 5'-UTR, causing an N-terminal extension of 45 amino acids. The existence of the RNA edited version is supported by direct protein sequencing by MS/MS of the following peptides specific to that version: 23-31 and 40-48. The RNA edited version is called ET-HMGN1. Belongs to the HMGN family.