H/ACA RNAs are small nuclear RNAs that have many different functions in the cell. They are guide RNAs for the conversion of the uridine into pseudouridine of ribosomal RNAs and spliceosomal snRNAs. We showed that box H/ACA RNAs directing modifications of spliceosomal snRNAs carry a special signal that direct these box H/ACA RNAs into Cajal bodies. This signal is also present in the telomerase RNA that accumulates in Cajal bodies. With fluorescent microscopy, we were able to propose that Cajal bodies may deliver telomerase RNA at a subset of telomeres in S phase cells. Finally, our work on the expression and processing of box H/ACA RNAs revealed that splicing and assembly of box H/ACA RNP particles are two independent molecular events in human cells.
