High-Mobility Group

HMGB2 belongs to the non-histone chromosomal high-mobility group protein family which are chromatin-associated and highly spread in the nucleus of higher eukaryotic cells. HMGB2 can successfully bend DNA and form DNA circles which indicates that HMGB2 facilitates cooperative interactions between cis-acting proteins by promoting DNA flexibility. Additionally, HMGB2 takes part in the final ligation step in DNA end-joining processes of DNA double-strand breaks repair and V(D)J recombination.

High-mobility group box 1 protein (HMGB1), previously known as HMG-1 or amphoterin, is a member of the high mobility group box family of non-histone chromosomal proteins. Human HMGB1 is expressed as a 30 kDa, 215 amino acid (aa) single chain polypeptide containing three domains: two N-terminal globular, 70 aa positively charged DNA-binding domains (HMG boxes A and B), and a negatively charged 30 aa C-terminal region that contains only Asp and Glu.4, 5 Residues 27 - 43 and 178 - 184 contain a NLS. Posttranslational modifications of the molecule have been reported, with acetylation occurring on as many as 17 lysine residues. HMGB1 is expressed at high levels in almost all cells. It was originally discovered as a nuclear protein that could bend DNA. Such bending stabilizes nucleosome formation and regulates the expression of select genes upon recruitment by DNA binding proteins.

High mobility group protein HMG-I/HMG-Y (HMGA1) belongs to the non-histone chromosomal high mobility group protein (HMG) family. HMGA1 is composed of a highly conserved AT-hook DNA-binding domain which mediates binding to AT-rich sequences in the minor groove of chromosomal DNA. HMGA1 functions as an architectural chromatin-binding transcription factor modifying the conformation of DNA by modulating nuclear protein-DNA complexes. Furthermore, HMGA1 is involved in numerous cellular processes including growth regulation, viral induction of beta-IFN gene and regulation of inducible gene transcription.

High Mobility Group Nucleosomal Binding Domain 3 (HMGN3), binds thyroid hormone receptor beta, however it occurs only in the presence of thyroid hormone. Thyroid hormone receptors are hormone-dependent transcription factors which regulate expression of a variety of particular target genes. HMGN3 is considered to reduce the compactness of the chromatin fiber in nucleosomes, in that way enhancing transcription from chromatin templates.

HMGN1 binds to the inner side of the nucleosomal DNA therefore changing the interaction between the DNA and the histone octamer. HMGN1 participates in the development which maintains transcribable genes in an exceptional chromatin conformation. HMGN1 inhibits the phosphorylation of nucleosomal histones H3 and H2A by RPS6KA5/MSK1 and RPS6KA3/RSK2.

HMGB3 is a member of the high mobility group (HMG) protein superfamily. HMGB3 holds DNA-binding HMG box domains, as do HMG1 and HMG2, and like the rest of the HMG protein superfamily members has a vital part in DNA replication, transcription and nucleosome assembly.

HMGB1 is an abundant chromatin-binding protein found in eukaryotic cell nucleus and acts in the assembly of nucleoprotein complexes. Inside the cell, HMGB1 binds to DNA and is involved in transcriptional regulation. Outside the cell, HMGB1 acts as a cytokine with activities that resemble those of tumor necrosis factor (TNF). HMGB1 is elevated significantly in chronic kidney disease patients and correlates with glomerular filtration rate as well as with markers of inflammation and malnutrition. HMGB1 is involved in Gram-negative sepsis by catalyzing movement of LPS monomers from LPS aggregates to CD14 to initiate a TLR4-mediated proinflammatory response. HMGB1 plays an important role in the relationship between necrosis and malignancy in glioma tumours. HMG1 protein is induced by Mycobacterium bovis BCG. Overexpression of HMGB1 is common in gastrointestinal stromal tumors and is related to the KIT mutation. HMG1 induces growth inhibition and apoptosis in macrophages through RAGE intracellular signaling pathway. The increase of extracellular HMGB1 observed in salivary glands of Sjogren's syndrome patients indicates that HMGB-1 is involved in the inflammatory process of the disease. HMGB-1 together with estrogen increase cell cycle progression in tumor cell lines.

High Mobility Group AT-Hook 2 (HMGA2) is a member of the non-histone chromosomal high mobility group (HMG) family. HMG proteins perform as architectural factors and are necessary components of the enhancesome. Thisprotein contains structural DNA-binding domains and may function as a transcriptional regulating factor. In addition, identification ofthe deletion, amplification, and rearrangement of this gene that are associated with myxoid liposarcoma proposes arole in adipogenesis and mesenchymal differentiation. A gene knock out study of the mouse counterpartdemonstrated that this gene is implicated in diet-induced obesit.Among the Diseases associated with HMGA2 are diffuse lipomatosis, and 12q14 microdeletion syndrome.