Beta-globin mRNAs capped with m7G, m2.7(2)G or m2.2.7(3)G differ in intrinsic translation efficiency.
We examined the intramolecular effect of altered cap structures on translation efficiency of artificial beta-globin mRNAs. For these studies, synthetic dinucleotides of the form X(5')ppp(5')G [X = 7-methyl guanosine (m7G), 2,7-dimethyl guanosine (m2(2,7)G) or 2,2,7-trimethyl guanosine (m3(2,2,7)G)], were transcriptionally incorporated into mRNAs, containing rabbit beta-globin coding sequences, using T7 RNA polymerase and a beta-globin cDNA template. These synthetic mRNAs were assayed in reticulocyte lysate for activity relative to m7G-capped mRNA. m2(2,7)G-Capped mRNA was found to be 1.5-fold more active than m7G-capped mRNA. Messenger RNA capped with m3(2,2,7)G was less active with activity of 0.24 relative to its m7G-capped counterpart (activity = 1.0). These data suggest that m7G-capped mRNAs become more active as translation templates after addition of a single N2 methyl moiety, which is especially pertinent to gene expression in togaviridae. The latter are observed to synthesize m2(2,7)G and m3(2,2,7)G-capped mRNAs in addition to m7G-capped templates during the course of infection in animal cells.
Darzynkiewicz
E
E
Department of Microbiology, USC School of Medicine, Los Angeles 90033-1054.
Stepinski
J
J
Ekiel
I
I
Jin
Y
Y
Haber
D
D
Sijuwade
T
T
Tahara
S M
SM
D000818:Animals; D002474:Cell-Free System; D005914:Globins / Q000235:genetics*; D066298:In Vitro Techniques; D008745:Methylation; D014176:Protein Biosynthesis; D012315:RNA Caps; D012333:RNA, Messenger / Q000235:genetics*; D011817:Rabbits; D013329:Structure-Activity Relationship
D012315:RNA Caps; D012333:RNA, Messenger; D005914:Globins