Expression and packaging of AluACA RNAs into box H/ACA RNPs

The AluACA RNAs are processed from intronic Alu repetitive sequences and they fold into the characteristic hairpin-hinge-hairpin-tail structure of box H/ACA snRNAs. The mature AluACA RNAs associate with the four H/ACA core proteins, dyskerin, Nhp2, Gar1 and Nop10 and the Cajal body-targeting protein Wdr79. Since Alu repetitive elements are confined to the primate genomes, the AluACA RNPs represent a human- or primate-specific group of box H/ACA RNPs.  Although the majority of  H/ACA RNPs function in site-specific RNA pseudouridylation, box H/ACA RNPs represent a functionally diverge group of snRNPs. The cellular function of AluACA RNPs remains unknown. Compared to canonical human box H/ACA RNAs, the AluACA RNAs possess atypical structural properties; they frequently carry unusually short 5’ hairpins and two closely placed Wdr79-binding sites.  Dissection of the biogenesis and cellular function of human AluACA RNPs provides a great challenge for our team.