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As the DNA template does not encode the 5' end cap, a synthetic cap analogue must be added to the mRNA. Cap analogs, which affect mRNA translation and transformation, are valuable tools for studying gene expression, and are often associated with therapy. Anti-reverse cap analog (ARCA) is a cap analog that produces immunogenic cap 0 for the production of capped transcripts during in vitro transcription.

Background of ARCAs Cap

As a platform technology, synthetic mRNA is increasingly used to express proteins needed in cell culture and even in vivo. The 5' cap of mRNA is an important feature that affects the stability and translation efficiency of mRNA, and ultimately affects the total protein content of mRNA expression. The capping of in vitro transcriptional mRNA is usually achieved by adding the corresponding dinucleotide cap analog to the reaction.

In the presence of cap dinucleotide, when the mRNA was blocked by transcription in vitro, it was found that m7GpppG cap analog could bind in two orientations, and only the correctly located derivatives, namely, m7G, were in the outer position and participated in the translation process. This has been solved by designing a modified cap analogue with O-CH3 replacing the 3'- or 2'- hydroxyl group of m7G, so it is called "ARCA".

Structural requirements for a cap analog to be incorporated into mRNA and to produce ARCAs.Fig.1 Structural requirements for a cap analog to be incorporated into mRNA and to produce ARCAs. (Warminski, 2017)

Features of ARCAs Cap

ARCA contains hydrogen (O-H substitution), fluorine (o-f substitution), sulfur (O-S substitution) or larger substituents. ARCA can only be inserted in the right direction to form mRNA. This kind of mRNAs has high translation efficiency in vitro and in cultured cells.

Generally speaking, the modification of ARCAs cap has the following purposes:

  • Disruption or even complete destruction of biological activity (e.g., inhibition of degradation by decapping enzymes);
  • Increased affinity for specific cap-binding proteins, thereby enhancing related biological activity;
  • New properties of cap like structures without interfering with mRNA biological activity.

Application of ARCAs Cap

As a therapeutic drug for gene therapy, mRNA has huge application potential. It has been applied in some ongoing clinical trials, which is the driving force for the development of new mRNA cap modification molecular tools and the construction of new cap-based molecular probes. Synthetic cap analogs are useful research tools that can facilitate the study of cap-related processes at the molecular level and in biochemical and biological experiments, and may even eventually lead to the development of new therapeutic methods.

Due to the excellent inhibitory properties of ARCA, such compounds can help to prepare mRNA transcripts with high translation activity. To date, ARCAs cap RNA synthesized by in vitro transcription has been widely used in the study of mRNA function and metabolism, in vitro protein synthesis and expression of exogenous mRNA in living cells.

What Can Creative Biolabs Offer?

Creative Biolabs provides products and services with promising quality and exceptional price. Our mRNA service allows researchers to customize synthesis and introduce modifications to produce transcripts that are best suited for downstream applications. Based on years of intensive research, we provide customized high-quality ARCAs cap mRNA synthesis services. mRNA can be generated by DNA template provided by customers, or we can provide all-round services from scratch. Please contact us for more information.


  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.
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