InterPro domain: IPR036570

The HORMA domain (for HOP1, REV7 and MAD2) is an about 180-240 amino acids region containing several conserved motifs. Whereas the MAD2 and the REV7 proteins are almost entirely made up of HORMA domains, HOP1 contains a HORMA domain in its N-terminal region and a Zn-finger domain, whose general arrangement of metal-chelating residues is similar to that of the PHD finger, in the C-terminal region. The HORMA domain is found in proteins showing a direct association with chromatin of all crown group eukaryotes. It has been suggested that the HORMA domain recognises chromatin states that result from DNA adducts, double-stranded breaks or non-attachment to the spindle and acts as an adaptor that recruits other proteins involved in repair [ 1 ].

Secondary structure prediction suggests that the HORMA domain is globular and could potentially form a complex beta-sheet(s) with associated alpha-helices [ 2 ].

Some proteins known to contain a HORMA domain are listed below:

• Eukaryotic HOP1, a conserved protein that is involved in meiotic-synaptonemal-complex assembly.
• Eukaryotic mitotic-arrest-deficient 2 protein (MAD2), a key component of the mitotic-spindle-assembly checkpoint [ 2 ].
• Eukaryotic REV7, a subunit of the DNA polymerase zeta that is involved in translesion, template-independent DNA synthesis.
• Fungal Atg13, adaptor protein for the Atg1 kinase complex [ 3 , 4 ].

1. The HORMA domain: a common structural denominator in mitotic checkpoints, chromosome synapsis and DNA repair. Trends Biochem. Sci. 23, 284-6
2. Dynamic feature of mitotic arrest deficient 2-like protein 2 (MAD2L2) and structural basis for its interaction with chromosome alignment-maintaining phosphoprotein (CAMP). J Biol Chem , 17658-17667
3. Conserved and unique features of the fission yeast core Atg1 complex. Autophagy 22, 1-10
4. Structure of the Atg101-Atg13 complex reveals essential roles of Atg101 in autophagy initiation. Nat Struct Mol Biol 292, 572-80