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. 2006 Jun;31(6):311-5.
doi: 10.1016/j.tibs.2006.04.002. Epub 2006 May 2.

How a Single Protein Complex Accommodates Many Different H/ACA RNAs

Free PMC article

How a Single Protein Complex Accommodates Many Different H/ACA RNAs

U Thomas Meier. Trends Biochem Sci. .
Free PMC article


More than 100 mammalian H/ACA RNAs form an equal number of ribonucleoproteins (RNPs) by associating with the same four core proteins. 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. Recent crystal structures of archaeal H/ACA protein complexes show how the same four proteins accommodate >100 distinct but related H/ACA RNAs and reveal that a spatial mutation cluster underlies dyskeratosis congenita, a syndrome of bone marrow failure.


Figure 1
Figure 1. Archaeal Gar1-Cbf5-Nop10 complex and mammalian classes of H/ACA RNAs
Crystal structure of the H/ACA protein complex of Gar1 (blue), Nop10 (red), and Cbf5 with its catalytic domain (green), PUA domain (cyan), and amino terminus (yellow). The alpha carbon backbones in ribbon diagram are shown through a surface rendering based on the atomic coordinates for the P. furiosus proteins deposited in the Protein Data Bank (accession code 2ey4) [4] and generated using PyMOL ( The amino (N) and carboxy (C) termini of the proteins and the catalytic aspartate (arrow, black ball and stick model) are indicated. A top view, with the RNA binding surface on top, and a side view are presented. The likely area and surface for binding of one hairpin of any of the depicted H/ACA RNAs are outlined by a grey dashed oval and a grey dashed line, respectively. In the RNA schematics, the location of antisense elements in the pseudouridylation pockets and the template region of telomerase RNA are highlighted (thick black lines). Note, relative to the protein complex, the H/ACA RNAs are not drawn to scale and are randomly arranged around the protein structures. The location of the DC mutation cluster in the Cbf5 PUA domain and amino terminus (based on a model of human NAP57) is pointed out by arrowheads.

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