mRNA 5' Capping

Background

At present, gene manipulation technology (DNA therapy) is gradually developed and widely used in industry and medicine. Due to the new progress of mRNA technology, RNA has become an attractive alternative for the development of DNA therapy, which can obtain particles with higher stability and translation efficiency. In recent years, Creative Biolabs has studied different modifications of mRNA cap structure to improve the properties of RNA.

• Introduction of mRNA 5' Cap
  All eukaryotic mRNA consists of a cap structure, an N7-methylguanosine, which is connected to the first nucleotide of the RNA by a reverse 5' to 5' triphosphate linkage. In addition to the important role of its cap-dependent protein synthesis promoter, the mRNA cap also serves as a protective group for exonuclease cleavage of 5' to 3' nucleic acids, and is the unique identifier for the recruitment of protein factors for pre-mRNA splicing, polyadenylation and nuclear output. It also functions as an anchor for the recruitment of promoters that initiate protein synthesis and the 5' to 3' looping of mRNA during translation. The mRNA 5' cap regulates splicing, nuclear output, resistance to exonuclease degradation, and initiation of translation. In short, 5' cap has the following functions:
  • Regulation of nuclear export;
  • Prevention of degradation by exonucleases;
  • Promotion of translation;
  • Promotion of 5' proximal intron excision.

Fig.1 An overview of RNA cap functions in gene expression and main proteins involved in cap recognition and metabolism.¹

• mRNA 5' Capping Process

In vivo, the cap 0 structure (m7G cap) can be further modified to cap 1 structure by adding methyl at the 2' O position of the mRNA initiating nucleotide. In about 50% of the transcripts, the additional 2'-O-methylation of the second nucleotide forms cap 2. Usually, the first nucleotide is adenosine, which can be methylated by N6 to form m6Am cap. Therefore, in addition to cap 0 intermediates, at least three endogenous cap structures, cap 1, cap 2 and m6Am cap, have been found in mature eukaryotic mRNA.

Fig.2 Structures of cap 0, cap 1, cap 2, and m6Am capped RNAs. B is any base.²

The starting point of capping with 7-methylguanylate is the unchanged 5' end of RNA molecule, which ends at the triphosphate group. It is characterized by the last nucleotide followed by three phosphate groups attached to the 5' carbon. Before transcription, the capping process begins with the synthesis of new pre-mRNA.

mRNA 5' Capping Services

Creative Biolabs provides a wide range of cap analogs for the application of co-transcriptional capping.

Highlights

• State-of-the-Art Capping Technology: Utilizing advanced enzymatic and co-transcriptional capping techniques, we ensure that the mRNA cap is structurally accurate and functionally optimal, closely mimicking natural mRNA processing.
• Customizable Capping Options: We offer various capping options, including Cap 0, Cap 1, and Cap 2 structures, allowing researchers to tailor the cap modification to specific experimental or clinical needs.
• Increased Immune Evasion: Properly capped mRNA can evade immune detection, making it ideal for therapeutic applications where minimal immunogenicity is crucial, such as in vaccine development and gene therapy.
• Comprehensive Quality Control: Each batch of capped mRNA undergoes rigorous quality control checks to guarantee the highest purity and activity, ensuring reliable results in downstream applications.

FAQ

Published Data

This document discusses the chemical synthesis and characterization of novel mRNA cap analogs designed to enhance translational efficiency and stability. These analogs, known as ARCA tetraphosphates, incorporate a phosphorothioate modification to decrease enzymatic degradation and a 2'-O-methyl group to ensure correct orientation during transcription. The study found that these modified cap structures significantly improve mRNA translation efficiency and stability, making them promising for RNA-based therapeutic applications such as gene therapy and anticancer vaccines.

Fig.3 The effect of different cap ends on the translation efficiency of mRNA.³

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References

1. Warminski, M.; et al. Applications of Phosphate Modification and Labeling to Study (m)RNA Caps. Topics in Current Chemistry. 2017, 375(1): 16-16.
2. Mccaffreyanton, P. RNA Epitranscriptome: Role of the 5' Cap. Genetic Engineering & Biotechnology News. 2019, 39(5).
3. Strenkowska, Malwina, et al. "Towards mRNA with superior translational activity: synthesis and properties of ARCA tetraphosphates with single phosphorothioate modifications." New Journal of Chemistry 34.5 (2010): 993-1007.