A. Summary	B. Nomenclature Changes	C. Literature Search Strategy	D. HMG Families	E. Canonical and Mammalian HMGs	F. Various HMGs	G. Plant HMGs

A.  Summary

The High Mobility Group (HMG) proteins were originally isolated from mammalian cells, named according to their electrophoretic mobility in polyacrylamide gels, and arbitrarily classed as a specific type of nonhistone proteins based on the observation that they are ubiquitous to mammalian cells, that they share certain physical properties,  and that they are associated with isolated chromatin. These mammalian proteins are considered to be Canonical HMG  proteins and are now subdivided into 3 families: the HMGB (formerly HMG-1/-2) family, the HMGN (formerly HMG-14/-17) family, and the HMGA (formerly HMG-I/Y/C) family.  Each HMG family has a characteristic functional sequence motif.  The functional motif of the HMGB family is called the "HMG-box;" that of the HMGN family, the  "nucleosomal binding domain;" and that of the HMGA family, the "AT-hook." The functional motifs characteristic of these canonical HMGs are widespread among nuclear proteins in a variety of organisms. Proteins containing any of these functional motifs embedded in their sequence are known as "HMG motif proteins."

B.  Nomenclature Changes

The New Nomenclature establishes a set of rules and a systematic way to name the genes and proteins belonging to the High Mobility Group (HMG) families of nuclear proteins. The HMG proteins are now subdivided into three families named HMGB, HMGA, and HMGN. The names of the genes correspond to the names of the encoded proteins. Within a family, the genes are named in sequential order (e.g., HMGB1, HMGB2). Splice variants are indicated by small letters (e.g., HMGA1a, HMGA1b and HMGA1c). The nomenclature has been devised to solve certain problems in mammalian genetic nomenclature; however the rules can be extended to other organisms. The new nomenclature now allows for a rational and complete search of the literature pertaining to HMG nuclear proteins. The interrelationship between the various mammalian HMG proteins is diagrammed below.

C.  Literature Search Strategy

Concomitant with the name changes, the search methods for HMG proteins have been modified in PubMed (ENTREZ) and alterations will be made in the MESH indexing. The old and new HMG names are both forward and backward search compatible. Thus, a PubMed search with a new term, "HMGB1", now, and in the future, will give the same result as a search with any of the old terms such as HMG1, HMG-1 or amphoterin. In the future, a search with HMG-14 will still give all the entries with text words such as either HMG-14, HMG14, or HMGN1 (see Table of HMG Proteins).  A search with HMGB, HMGN, or HMGA will yield entries for all the members of that HMG family. These options were not available prior to the name change and a search with the term "HMG" would have yielded many hits, >70% of them not related to the canonical HMG nuclear proteins.  Note that the old search strategy is still available and may be useful for certain searches.

D.  HMG Families

1. The HMGB Family  (formerly HMG-1/-2)
2. The HMGN Family  (formerly HMG-14/-17)
3. The HMGA Family  (formerly HMG-I/Y; HMGI-C)

E.  Canonical and Mammalian HMGs

F. Various HMGs

G.  Plant HMGs