This entry includes Rna14 from yeasts, protein suppressor of forked (su(f)) from Drosophila melanogaster, CSTF3 from animals and CstF77 from Arabidopsis. In budding yeasts, Rna14 is part of the cleavage factor I A (CF IA) complex and is required for both the cleavage and polyadenylation activities of CF IA []. Protein suppressor of forked may have similar function [, ]. CstF77 is involved in floral repressor gene (FLC) silencing [].
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 []. The HAT motif has striking structural similarities to HEAT repeats (), 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 [, ]. However, the HAT repeats of Arabidopsis HCF107 protein have been shown to bind RNA []. Proteins containing this domain includes:Crooked neck (Crn) from Drosophila. It associates with the RNA-binding protein HOW to control glial cell maturation []. Clf1, Prp6 and Prp39 from S. cerevisiae. Clf1 is part of the of the NineTeen Complex (NTC) that stabilises U6 snRNA in catalytic forms of the spliceosome containing U2, U5, and U6 snRNAs [, ]. Prp6 and Prp39 are involved in pre-mRNA splicing.Cleavage stimulation factor subunit 3 (CSTF3 or CstF-77) and crooked neck-like protein 1 (CRNKL1) from mammals. CSTF3 is required for polyadenylation and 3'-end cleavage of mammalian pre-mRNAs []. Protein high chlorophyll fluorescent 107 (HCF107) from Arabidopsis. HCF107 exhibits sequence-specific RNA binding and RNA remodeling activities, probably leading to the activation of translation of the target gene cluster psbB-psbT-psbH-petB-petD []. It blocks 5'-3' and 3'-5' exoribonucleases (e.g. polynucleotide phosphorylase (PNPase), RNase R) in vitro []. It is necessary for intercistronic RNA processing of the psbH 5' untranslated region or the stabilization of 5' processed psbH RNAs and is also required for the synthesis of psbB [, , ].
