Mechanism of RNA modifications » Enzymes  |  snoRNAs

Enzymes 

RNA modification is a dynamic process which occurs under the function of some enzymes whose action is similar to that of "writers". RNA modifications are placed under 3 groups, namely methylation that contains ribosomal methylation, base methylation and mixed methylation, pseudouridine and hypoxanthine respectively.

The overview of RNA modification sites guided by enzymes as follows:

ADAR FBL METTL14 METTL3 NOP56 NOP58 NSUN2 PUS1 RBM15B RBM15 WTAP
RNA editing Nm m6A m6A Nm Nm m5C Pseudo m6A m6A m6A
1462 1894 1504 1726 1306 1863 29 25 8404 13565 573

snoRNAs 

C/D box snoRNAs

The C/D box snoRNAs carry two conserved boxes, C box with 'RUGAUGA' in 5' end and D box with 'CUGA' in 3' end. While C'/D' box, the copies of C/D box are usually inside snoRNAs.
C/D box snoRNA binds to proteins to form complexes, snoRNPs, that catalyze RNA modifications. These proteins include FBL, NOP56, NOP5/NOP58 and NHPX. C/D box snoRNAs guide 2'-O-ribose methylation of target RNAs by upstream components of D/D' box.

H/ACA box snoRNAs

The H/ACA box snoRNAs contain two hairpins and two single-stranded regions. The single-stranded regions contain H box with 'ANANNA' internally and ACA box with 'ACA' in 3' end. While the bulges of hairpins bind to target RNA and guide pseudouridine modification of specific loci.
H/ACA box snoRNA binds to four proteins, including dyskerin, GAR1, NHP2 and NOP10 to guide pseudouridine methylation of target RNAs.

Cajal body-specific scaRNAs

The Cajal body-specific scaRNAs have more complex chemical structure that offen contain both C/D box and H/ACA box. They can guide modifications of snRNA, like U1, U2, U4 and U5 that transcribed by polymerase II.


The overview of RNA modification sites guided by snoRNAs as follows:

Human Mouse Yeast Fly C.elegans Zebrafish A.thaliana
Pseudo 1574 659 98 342 144 5 28
Am 631 127 42 174 40 9 26
Cm 390 66 22 76 55 0 26
Gm 826 85 35 143 28 18 17
Um 185 37 23 48 25 11 33

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