High-mobility group

High-Mobility Group or HMG is a group of chromosomal proteins that help with transcription, replication, recombination, and DNA repair.

Families
The HMG proteins are subdivided into 3 superfamilies each containing a characteristic functional domain:


 * HMGA – contains an AT-hook domain
 * HMGA1
 * HMGA2


 * HMGB – contains a HMG-box domain
 * HMGB1
 * HMGB2
 * HMGB3
 * HMGB4


 * HMGN – contains a nucleosomal binding domain domain
 * HMGN1
 * HMGN2
 * HMGN3
 * HMGN4


 * Sex-Determining Region Y Protein


 * TCF Transcription Factors
 * Lymphoid enhancer-binding factor 1
 * T Cell Transcription Factor 1

Proteins containing any of these embedded in their sequence are known as HMG motif proteins. HMG-box proteins are found in a variety of eukaryotic organisms.

They were originally isolated from mammalian cells, and named according to their electrophoretic mobility in polyacrylamide gels.

Function
HMG proteins are thought to play a significant role in various human disorders. Disruptions and rearrangements in the genes coding for some of the HMG proteins are associated with some common benign tumors. Antibodies to HMG proteins are found in patients suffering from autoimmune diseases. The SRY gene on the Y Chromosome, responsible for male sexual differentiation, contains an HMG-Box domain. Recently, a member of the HMG family of proteins, HMGB1, has been shown to have an extracellular activity as a chemokine, attracting neutrophils and mononuclear inflammatory cells to the infected liver.