CHROMO

Chromatin organization modifier domain
CHROMO
SMART accession number:SM00298
Description: -
Interpro abstract (IPR000953):

The CHROMO (CHRromatin Organization MOdifier) domain [ (PUBMED:1982376) (PUBMED:1708124) (PUBMED:7667093) (PUBMED:7501439) ] is a conserved region of around 60 amino acids, originally identified in Drosophila modifiers of variegation. These are proteins that alter the structure of chromatin to the condensed morphology of heterochromatin, a cytologically visible condition where gene expression is repressed. In one of these proteins, Polycomb, the chromo domain has been shown to be important for chromatin targeting.

Proteins that contain a chromo domain appear to fall into 3 classes. The first class includes proteins having an N-terminal chromo domain followed by a region termed the chromo shadow domain, with weak but significant sequence similarity to the N-terminal chromo domain,[ (PUBMED:7667093) ], eg. Drosophila and human heterochromatin protein Su(var)205 (HP1). The second class includes proteins with a single chromo domain, eg. Drosophila protein Polycomb (Pc); mammalian modifier 3; human Mi-2 autoantigen and several yeast and Caenorhabditis elegans hypothetical proteins. In the third class paired tandem chromo domains are found, eg. in mammalian DNA-binding/helicase proteins CHD-1 to CHD-4 and yeast protein CHD1.

Functional dissections of chromo domain proteins suggests a mechanistic role for chromo domains in targeting chromo domain proteins to specific regions of the nucleus. The mechanism of targeting may involve protein-protein and/or protein/nucleic acid interactions. Hence, several line of evidence show that the HP1 chromo domain is a methyl-specific histone binding module, whereas the chromo domain of two protein components of the drosophila dosage compensation complex, MSL3 and MOF, contain chromo domains that bind to RNA in vitro [ (PUBMED:11574148) ].

The high resolution structures of HP1-family protein chromo and chromo shadow domain reveal a conserved chromo domain fold motif consisting of three beta strands packed against an alpha helix. The chromo domain fold belongs to the OB (oligonucleotide/oligosaccharide binding)-fold class found in a variety of prokaryotic and eukaryotic nucleic acid binding protein [ (PUBMED:11574148) ].

Family alignment:
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There are 41552 CHROMO domains in 32518 proteins in SMART's nrdb database.

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