5'-N7-Methylguanosine-triphosphate (mCap)

The 5' N7-Methylguanosine-triphosphate Cap

All newly formed eukaryotic RNA transcripts undergo a number of post-translational modifications before they are transferred into the cytoplasm. Eukaryotic mRNAs are initially transcribed by RNA polymerase II as direct copies of a gene that include several non-coding sequences such as introns. A nuclear RNA molecule experiences three main events during its life:

1. The addition of a 5' cap: N⁷-Methylguanosine-triphosphate Cap,
2. The addition of a 3' poly A tail,
3. The removal of unwanted intronic sequence by a process called RNA splicing.

The majority of eukaryotic and viral messenger RNAs as well as small nuclear (snRNA) and small nucleolar RNAs (snoRNAs) involved in nuclear RNA processing are capped at the 5’end with the cap structure 5′ N7-Methylguanosine-triphosphate (7mGpppN). The cap at the 5′-terminus is required for processing and maturation of the RNA transcript in the nucleus. The methylated RNA cap is also needed to transport the message from the nucleus to the cytoplasm, ensures mRNA stability and efficient translation of the message into a protein. Synthetic RNA oligonucleotides that are modified with the 5′-N7-MeGppp cap can act as substrates and mimick cellular capped mRNAs. The synthetic 5′-N7-MeGppp oligonucleotide cap can be used for various biochemical and structural studies. Scientists have demonstrated that the cap structure can inhibit the influenza and flavivirus RNA Polymerases.
 

Oligonucleotide synthesis and purification of 5' N7-Methylguanosine-triphosphate Cap 7mGppp, mRNA Cap

Capped RNA oligonucleotides can be synthesized enzymatically by in vitro transcription and chemically using phosphoramidite chemistries. The use of chemical synthesis allows reproducibly obtaining capped RNAs at almost any scale independent from the RNA sequences and allows the addition of modifications at specific positions as well. The resulting modified oligonucleotides can be purified to a high purity and analyzed by a number of established methods, including PAGE, reverse phase HPLC, anion-exchange HPLC and mass-spectrometry. Since free 2’, 3’-hydroxyls can form complexes with borate ions, caps or capped oligonucleotides can be purified by affinity chromatography using substrates such as dihydroxyboryl-cellulose. Treatment with periodate allows to oxidize the cis-diols to dialdehyde which can then be reduced with borohydrate to label the terminus for example with fluorophores.

Bio-Synthesis also offer capped RNA oligonucleotides that contain guanosine instead of 7-methylguanosine. For more information on Capped Oligonucleotide Synthesis

References:

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