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Almost all eukaryotic cellular mRNAs and many viral RNAs possess a modified nucleotide structure (N⁷-methyl guanosine, m⁷G) at their 5'-end, known as "Cap". This Cap plays an important role during various stages of gene expression including mRNA splicing^[1], intracellular transport^[2], turnover and, translation^[3,4].

For synthesis of 5'-capped RNAs with in vitro transcription catalyzed by viral RNA polymerases, typically a standard Cap analog such as m⁷G(5')p3G is used for incorporation (Figure 1A). Since however, these simple Cap analogs are incorporated into the RNA both in the forward [m⁷G(5')p₃G(pN)] and the reverse orientation [G(5')p₃m⁷G(pN)] this leads to two forms of isomeric RNAs^[5]. RNAs capped with reverse 5'-Caps are poorly translated and more readily degraded.

Therefore, Anti-reverse cap analogs (ARCAs), such as m₂^7.3'-OGp₃G (Figure 1B) carrying a 3'-O-methyl group have been developed^[6,7,8]. They are incorporable in the correct (i.e. forward) orientation only and were shown to yield RNA transcripts that are more efficiently translated in vitro.

Jena Bioscience makes ARCA cap m₂^7.3'-OGpppG available:

• from mg to g scale
• with a purity of >98 % (HPLC)
• at a price that has been significant reduced:

Product	Cat. No.	Amount	Price
m27.3'-OGP3G (ARCA Cap Analog)	NU-855-1	1 mg pack	98 €
	NU-855-5	5 mg pack	443 €

Also available are the standard cap analogs:

• GpppG (unmethylated cap analog) – Cat. No. NU-854
• m⁷GpppG (monomethylated cap analog) – Cat. No. NU-852
• m₃^2.2.7GpppG (trimethylated cap analog) – Cat. No. NU-853

For more information please see: www.jenabioscience.com/cms/en/1/catalog/2051

Selected References
[1] Izaurralde et al. (1994) A nuclear cap binding protein complex involved in pre-mRNA splicing. Cell 78(4):657.
[2] Jacobson et al. (1998) A 7-methylguanosine cap commits U3 and U8 small nuclear RNAs to the nucleolar localization pathway. Nucl. Acids. Res. 26(3):756.
[3] Gingras et al. (1999) eIF4 initiation factors: effectors of mRNA recruitment to ribosomes and regulators of translation. Annu. Rev. Biochem. 68:913.
[4] Rhoads (2009) eIF4E: New family members, new binding partners, new roles. J. Biol. Chem. 284(25):16711.
[5] Pasquinelli et al. (1995) Reverse 5' caps in RNAs made in vitro by phage RNA polymerases. RNA 1:957.
[6] Peng et al. (2002) Synthesis and application of a chain-terminating dinucleotide mRNA cap analog. Organic Letters 4:161.
[7] Stepinski et al. (2001) Synthesis and properties of mRNAs containing the novel "anti-reverse" cap analogues 7-methyl(3'-O-methyl)GpppG and 7-methyl(3'-deoxy)GpppG. RNA 7:1486.
[8] Jemielity et al. (2010) Synthetic mRNA cap analogs with a modified triphosphate bridge – synthesis, applications and prospects. New J. Chem. 34:829.

Nucleotide analogs not on stock may be available as custom synthesis, just send us an e-mail at nucleotides@jenabioscience.com with any questions you may have!