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Number of (2 major) modifications to pre-rRNA: methyl group additions and pseudouridylation

Range	67 2'-O-ribose methylations: 44 pseudouridylations modifications
Organism	Budding yeast Saccharomyces cerevisiae
Reference	Woolford JL Jr, Baserga SJ. Ribosome biogenesis in the yeast Saccharomyces cerevisiae. Genetics. 2013 Nov195(3):643-81. doi: 10.1534/genetics.113.153197. p.649 left column 3rd paragraphPubMed ID24190922
Primary Source	Balakin, A. G., L. Smith, and M. J. Fournier, 1996 The RNA world of the nucleolus: two major families of small RNAs defined by different box elements with related functions. Cell 86: 823–834. & Kiss-Laszlo, Z., Y. Henry, J. P. Bachellerie,M. Caizergues-Ferrer, and T. Kiss, 1996 Site-specific ribose methylation of preribosomal RNA: a novel function for small nucleolar RNAs. Cell 85: 1077–1088. & Ganot, P., M. L. Bortolin, and T. Kiss, 1997 Site-specific pseudouridine formation in preribosomal RNA is guided by small nucleolar RNAs. Cell 89: 799–809. & Liang, X. H., Q. Liu, and M. J. Fournier, 2009 Loss of rRNA modifications in the decoding center of the ribosome impairs translation and strongly delays prerRNA processing. RNA 15: 1716–1728. & Watkins, N. J., and M. T. Bohnsack, 2012 The box C/D and H/ACA snoRNPs: key players in the modification, processing and the dynamic folding of ribosomal RNA. Wiley Interdiscip. Rev. RNA 3: 397–414.PubMed ID8797828, 8674114, 9182768, 19628622, 22065625
Comments	"The two major classes of snoRNPs that modify the prerRNA are named for their respective conserved snoRNA sequence motifs (Kiss et al. 2010 Watkins and Bohnsack 2012). The box H/ACA snoRNPs catalyze pseudouridylation at 44 sites on the rRNA, while the box C/D snoRNPs catalyze 2'-O-ribose methylation at 67 sites (primary sources) (Figure 6 figure - link ). For each class of snoRNPs, catalysis is carried out by an enzyme stably associated with the snoRNA and is guided by a short snoRNA sequence."
Entered by	Uri M
ID	110020