In molecular biology, the HMG-box (high mobility group box) is a protein domain which is involved in DNA binding.

[1] The domain is composed of approximately 75 amino acid residues that collectively mediate the DNA-binding of chromatin-associated high-mobility group proteins.

HMG-boxes are present in many transcription factors and chromatin-remodeling complexes, where they can mediate non-sequence or sequence-specific DNA binding.

[1] HMG-box domains are found in some high mobility group proteins, which are involved in the regulation of DNA-dependent processes such as transcription, replication, and DNA repair, all of which require changing the conformation of chromatin.

[3] The single and the double box HMG proteins alter DNA architecture by inducing bends upon binding.