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Reference.org
Small nucleolar RNA U3
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<p>In <a href="/facts/Molecular_biology/YgqU35ub">molecular biology</a>, U3 snoRNA is a <a href="/facts/Non-coding_RNA/aXqyV5so">non-coding RNA</a> found predominantly in the <a href="/facts/Nucleolus/X7B5HKM4">nucleolus</a>. U3 has <a href="/facts/Small_nucleolar_RNA/lcWShLfJ">C/D box motifs</a> that technically make it a member of the box C/D class of <a href="/facts/SnoRNA/lcWShLfJ">snoRNAs</a>; however, unlike other C/D box snoRNAs, it has not been shown to direct 2'-<i>O</i>-<a href="/facts/Methylation/EvDMWVW5">methylation</a> of other RNAs. Rather, U3 is thought to guide site-specific cleavage of <a href="/facts/Ribosomal_RNA/zy5FxddY">ribosomal RNA</a> (rRNA) during pre-rRNA processing. </p><p>The box C/D element is a subset of the six short sequence elements found in all U3 snoRNAs, namely boxes A, A', B, C, C', and D. </p>