Cell-type capping

RNAs are capped by a viral reaction similar to that in the cell. GTP is first covalently bound to GTase as GTase-GMP, which is then transferred to the processed ppRNA to form a GpppN RNA. The RNA is further N7-methylated and 2'O-methylated by two other viral enzymes.

image (RNA TPase=RNA triphosphatase, RdRp=RNA-dependent RNA polymerase, GTase=guanylyltransferase, MTase=methyltransferase, SAM= S-adenosylmethionine, SAH= S-adenosylhomocysteine)

Enzymatic reactions
RNA triphosphatase: Rhea 67004
Guanylyl transfer on viral RNA: Rhea 67012
N7 Methyltransferase: Rhea 67008
2'O Methyltransferase: Rhea 67020

virusRNA TPase
Rhea 67004
GTase
Rhea 67012
N7MTase
Rhea 67008
2'O methylase
Rhea 67020
Host metazoanRNGTT: CysPhos-TPaseRNGTT
(GTase-Lys-GMP)
RMNT (Ross)CMTR1
IridovirusORF064L: CysPhos-TPaseORF064L
(GTase-Lys-GMP)
235L?235L?
BaculovirusLEF-4: TTM-TPaseLEF-4
(GTase-Lys-GMP)
UnknownAc69
PTP/BVP: CysPhos-TPase
Vaccinia (Poxvirus)D1R: TTM-TPaseD1R
(GTase-Lys-GMP)
D1R: TTM TPase +D12L J3R
Orthoflavivirus (Dengue virus)NS3: Flavi-TPaseNS5 + SLA RNA
(GTase-Arg-GMP)
NS5 + SLA RNA NS5 + SLA RNA
Mammalian orthoreovirusMu2? Lambda1? Lambda2
(GTase-Lys-GMP)
Lambda2Lambda2
Orbivirus(Bluetongue virus)VP4: VP4
(GTase-Lys-GMP)
VP4 VP4

Host protozoan, fungiCET1: TTM-TPaseCEG1
(GTase-Lys-GMP)
ABD1None
ChlorellavirusA449R: TTM-TPaseA103R
(GTase-Lys-GMP)
UnknownNone?
MimivirusMimiCE: TTM-TPase MimiCE
(GTase-Lys-GMP)
MimiCENone


Mimivirus TPase
Paramecium bursaria chlorella virus (PBCV-1) GTase
in complex with cap analog GPPPG
Vaccinia methyltransferase OPG102 complexed with M7G capped RNA hexamer.