In molecular biology, Small nucleolar RNA sR8 is a non-coding RNA belonging to the C/D box class of snoRNAs. sR8, along with other C/D box snoRNAs, performs 2โฒ-O-methylation of ribose on a target strand of ribosomal RNA.[1][2] Targeting is achieved through the C and D box components, which are short sections of conserved sequences, as well as C'/D' boxes (internal equivalents of the C and D boxes). These sequences base-pair with nucleotides in the target rRNA to direct their methylation.[3]
sR8 RNA operates alongside protein components in a ribonucleoprotein (RNP) complex. sR8 is able to guide the methylation of targets found within structured stem-loops, which implies that a component of the complex is able to unwind such structures.[3]
As a model system
sR8 is considered a 'model'[3] C/D box sRNA and has been used in several experiments investigating the nature of C/D box snoRNAs and ribonucleoprotein complexes.[4][5] It is particularly useful in studies because the RNP can be entirely constructed in vitro.[3]
sR8 RNA from the hyperthermophileMethanocaldococcus jannaschii has been used to elucide the 3-dimensional structure of a C/D box RNP.[6] The structure was unexpectedly found to be dimeric, wherein two RNA molecules bind with several proteins in the same complex.[6][7]
^Rashid R, Aittaleb M, Chen Q, Spiegel K, Demeler B, Li H (October 2003). "Functional requirement for symmetric assembly of archaeal box C/D small ribonucleoprotein particles". J. Mol. Biol. 333 (2): 295โ306. doi:10.1016/j.jmb.2003.08.012. PMID14529617.
