InterPro domain: IPR036756

H/ACA ribonucleoprotein particles (RNPs) are a family of RNA pseudouridine synthases that specify modification sites through guide RNAs. The function of these H/ACA RNPs is essential for biogenesis of the ribosome, splicing of precursor mRNAs (pre-mRNAs), maintenance of telomeres and probably for additional cellular processes [ 1 ]. All H/ACA RNPs contain a specific RNA component (snoRNA or scaRNA) and at least four proteins common to all such particles: Cbf5, Gar1, Nhp2 and Nop10. These proteins are highly conserved from yeast to mammals and homologues are also present in archaea [ 2 ]. The H/ACA protein complex contains a stable core composed of Cbf5 and Nop10, to which Gar1 and Nhp2 subsequently bind [ 3 ].

In eukaryotes Nop10 is a nucleolar protein that is specifically associated with H/ACA snoRNAs. It is essential for normal 18S rRNA production and rRNA pseudouridylation by the ribonucleoprotein particles containing H/ACA snoRNAs (H/ACA snoRNPs). Nop10 is probably necessary for the stability of these RNPs [ 4 ]. The Nop10 domain structure has a rubredoxin-like fold.

1. How a single protein complex accommodates many different H/ACA RNAs. Trends Biochem. Sci. 31, 311-5
2. Evolutionary appearance of genes encoding proteins associated with box H/ACA snoRNAs: cbf5p in Euglena gracilis, an early diverging eukaryote, and candidate Gar1p and Nop10p homologs in archaebacteria. Nucleic Acids Res.
3. The box H/ACA ribonucleoprotein complex: interplay of RNA and protein structures in post-transcriptional RNA modification. J. Biol. Chem. 28, 2342-52
4. Nhp2p and Nop10p are essential for the function of H/ACA snoRNPs. EMBO J. 17, 7078-90