ARCA Cap in RNA Research and Therapeutics
The cap structure at the 5′ end of eukaryotic mRNA is composed of a methylated guanosine nucleoside that is connected to the rest of the mRNA via a 5′–5′ triphosphate linkage. This cap plays a key role in regulating the export of mRNA from the nucleus and protecting it from digestion by exonucleases. It also enables efficient translation by facilitating the binding of a transcription initiation factor. Consequently, the mRNA cap is essential for translation.
The ARCA cap is an artificial mRNA cap frequently used for co-transcriptional capping of in vitro transcribed (IVT) mRNA. Similar to its natural counterpart, it protects the mRNA from exonuclease attack and enables efficient translation by facilitating the binding of a transcription initiation factor.
The anti-reverse cap analogue (ARCA) is considered a next-generation tool in mRNA research because it improves the efficiency and reliability of synthetic mRNA. Unlike conventional cap analogues, ARCA ensures that the cap is incorporated only in the correct orientation, which enhances mRNA stability and translation efficiency. This makes ARCA especially valuable for applications such as mRNA therapeutics, vaccines, and protein expression studies, where high yield and consistent performance are critical.
What is ARCA Cap
An anti-reverse cap analogue – ARCA – is a chemically modified dinucleotide used to cap synthetic mRNA during in vitro transcription. Like the natural 5′ cap of eukaryotic mRNA, it protects the RNA from degradation and supports efficient translation. The modification prevents the cap from being incorporated in the “reverse” orientation, which would render the mRNA unfunctional.
The ARCA cap consists of a guanosine nucleoside (1) that is methylated at position 7 (m⁷G), which is connected to a second guanosine (2) via a 5′–5′ triphosphate linkage (3). The 3′ hydroxyl (OH) group of the ribose sugar (4) of the m7G nucleoside is also methylated. This methylation prevents the formation of a bond between the 3´-OH group of m7G and the rest of the mRNA during in vitro-transcription, therefore ensuring its incorporation in the correct direction into the nascent mRNA.
Figure 1. Structural formula of m27,3′-OGP3G (ARCA cap analog)
Classical cap analogues, like the first-generation m7GpppG, can be incorporated at the 5′ end of mRNA in both forward and reverse orientations during in vitro transcription. Only the forward orientation supports efficient translation, while the reverse orientation results in non-functional transcripts. ARCA cap contains a structural modification that prevents reverse incorporation, ensuring that all capped transcripts are oriented correctly and fully functional.
The Role of ARCA Cap in mRNA Translation
ARCA cap improves translation efficiency by ensuring that the 5′ cap is incorporated in the correct orientation during in vitro transcription. This correct orientation allows efficient recognition by the eukaryotic initiation factor eIF4E, leading to enhanced ribosome recruitment and higher protein production.
Conventional cap analogues can be incorporated in both forward and reverse orientations, but only the forward orientation is functional for translation. ARCA contains a chemical modification that prevents reverse incorporation by RNA polymerases, ensuring that all capped transcripts are functional. ARCA modifies the 3′ hydroxyl group of the m⁷G nucleotide, converting it into a 3′ O-methyl group. This substitution removes the free hydroxyl group necessary for phosphodiester bond formation in the reverse orientation. Without this reactive group, RNA polymerase is unable to extend the RNA chain from the m⁷G in the reverse direction. Consequently, only the correct 5′ to 3′ orientation is chemically viable during transcription. This ensures that all synthesized mRNA molecules are properly capped, thereby improving translation efficiency and increasing the stability of the transcripts.
Synthetic mRNA is widely used in research and medicine, including applications such as mRNA vaccines, cancer immunotherapy, protein replacement therapies, and cell reprogramming. The use of ARCA-capped mRNA enhances the stability and translational efficiency of these therapeutic molecules.
Enhanced mRNA Stability and Performance
The ARCA cap protects the mRNA from rapid degradation by 5′ exonucleases, extending its half-life in cells. This stabilization allows more time for translation and increases the overall yield of the encoded protein.
Unlike natural cap analogues, the ARCA cap eliminates the possibility of reverse orientation, leading to more uniform and predictable mRNA populations. This results in higher translational output and more consistent experimental outcomes.
For mRNA therapeutics, stability and efficient translation are critical factors. ARCA cap contributes to both, making it an essential component in the development of vaccines, personalized cancer treatments, and other mRNA-based therapeutics.
ARCA Cap Product by baseclick
Do you need a properly capped mRNA construct from your in vitro transcription reaction? baseclick’s ARCA cap reagent guarantees the highest quality mRNA due to its exceptional purity. For added convenience, baseclick offers an in vitro transcription kit containing all enzymes and reagents for producing large quantities of ARCA-capped, functional mRNA. Looking for customized mRNA? With a wide variety of artificial cap structures to choose from, including ARCA, baseclick’s mRNA service can help optimize the stability and translation performance of your mRNA.
Besides ARCA cap, baseclick offers a wide variety of cap analoga for co-transcriptional capping of IVT-generated mRNA. For post-transcriptional 5´-modification via click chemistry or NHS esters, baseclick has a portfolio of optimized cap analoga containing an azide–, alkyne, or amino moiety to meet the specific needs of our customers.
- Learn more about Click Chemistry Glossary here: Click Chemistry
Custom Solutions for Research and Development
baseclick’s mRNA service enables the generation of customized mRNA constructs for specific research and clinical development applications. Feel free to check the broad range of modifications and bioconjugation ligands available to further customize your ARCA-capped mRNA.
- Learn more about mRNA Service
Our team of scientific experts has over fifteen years’ experience in nucleic acid chemistry and is dedicated to supporting our clients throughout their projects, from initial consultation to practical assistance. Please feel free to contact us for further information.
Why Choose baseclick for ARCA Cap Reagents?
baseclick has been at the forefront of click chemistry since its early development — a concept that won the Nobel Prize in Chemistry in 2022. We offer a wide range of click chemistry products, including chemical reagents and advanced kits for various biological applications and drug development. We also provide custom oligonucleotide and mRNA production services.
In collaboration with the Ludwig Maximilian University of Munich and as part of the Cluster for Nucleic Acid Therapeutics, baseclick transforms fundamental research into state-of-the-art assay kits and chemicals for the conjugation of chemical entities to nucleic acids. As an ISO 9001:2015-certified company, we are proud to provide our customers with the highest-quality, most effective products in the field of click chemistry.
Since 2022, baseclick has offered the option to purchase in vitro-generated mRNA for research and clinical applications through its mRNA service. With a wide variety of possible modifications to choose from and the option to create highly customized, conjugated mRNA, our mRNA service is the perfect choice for acquiring high-quality, pure, ready-to-use mRNA in just a few days.
Unlocking RNA Potential with ARCA Cap
Taken together, ARCA cap enhances translation efficiency by promoting correct cap orientation, improves mRNA stability by protecting against exonuclease degradation, and ensures a more uniform population of functional transcripts. These properties make it particularly valuable for both research applications and the development of mRNA-based therapeutics, where high yield and reproducibility are essential.
Would you like any further technical assistance or scientific consultations? If so, please contact our team of nucleic acid experts, who will support you throughout your projects, from the initial consultation stage to providing practical assistance.
Are you interested in other mRNA cap-related products? Please visit our website for more information on the various 5´ mRNA capping options available, including capping with ARCA or CleanCap, and capping with modified cap analogues featuring molecular handles for subsequent 5´ ligation via click chemistry.