mRNA of eucaryon and virus has a monomethylated cap structure, m7G(5')ppp(5')G or called mCAP, at the 5’-initiating terminal. The cap analog plays an important role in cellular processes, the initiation of protein synthesis, protecting RNA from exonuclease cleavage, uniquely recognition for recruiting protein factors for pre-mRNA splicing, polyadenylation and nuclear export. The cap could interact with different binding proteins, initiation factors and elements of ribosomes.
mCAP is the first cap analog for the molecular biology toolbox. MCAP inserts in the correct orientation to enhance translation with a 50% chance. The other 50% of molecules can’t be a substrate for efficient translation, reducing the specific activity of the transcript.
mCAP can be incorporated in a transcription by including a mixture of the cap analog and GTP (usually at a 4:1 ratio). Approximately 80% of synthesized mRNA will possess a 5’ cap, while the remaining 20% will possess a 5’ triphosphate.
References:
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