The HAT (Half A TPR) repeat is found in several RNA processing proteins .
The HAT (Half A TPR) repeat has a repetitive pattern characterised by three aromatic residues with a conserved spacing. They are structurally and sequentially similar to TPRs (tetratricopeptide repeats), though they lack the highly conserved alanine and glycine residues found in TPRs. The number of HAT repeats found in different proteins varies between 9 and 12. HAT-repeat-containing proteins appear to be components of macromolecular complexes that are required for RNA processing [PUBMED:9478129]. The HAT motif has striking structural similarities to HEAT repeats (INTERPRO), being of a similar length and consisting of two short helices connected by a loop domain, as in HEAT repeats. Some studies have suggested that the HAT repeats may be involved in protein-protein interactions [PUBMED:19515729, PUBMED:18725399]. However, the HAT repeats of Arabidopsis HCF107 protein have been shown to bind RNA [PUBMED:22451905].