A Dimeric Structure for Archaeal Box C/D Small Ribonucleoproteins
Franziska Bleichert,1
Keith T. Gagnon,2
Bernard A. Brown, II,2
E. Stuart Maxwell,2
Andres E. Leschziner,3
Vinzenz M. Unger,4
Susan J. Baserga1,4,5,*
Methylation of ribosomal RNA (rRNA) is required for optimal
protein synthesis. Multiple 2'-O-ribose methylations are carried
out by box C/D guide ribonucleoproteins [small ribonucleoproteins
(sRNPs) and small nucleolar ribonucleoproteins (snoRNPs)], which
are conserved from archaea to eukaryotes. Methylation is dictated
by base pairing between the specific guide RNA component of
the sRNP or snoRNP and the target rRNA. We determined the structure
of a reconstituted and catalytically active box C/D sRNP from
the archaeon
Methanocaldococcus jannaschii by single-particle
electron microscopy. We found that archaeal box C/D sRNPs unexpectedly
formed a dimeric structure with an alternative organization
of their RNA and protein components that challenges the conventional
view of their architecture. Mutational analysis demonstrated
that this di-sRNP structure was relevant for the enzymatic function
of archaeal box C/D sRNPs.
2 Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA.
3 Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
4 Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA.
5 Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA.
* To whom correspondence should be addressed. E-mail: susan.baserga{at}yale.edu
