mRNA Capping

The in vitro modification process becomes critical when developing mRNA products. mRNA vaccines or drugs require the formation of a cap structure for stable expression in vivo. BOC Sciences' team has extensive experience in mRNA design and production and offers mRNA 5'-end capping services to meet the needs of our customers' projects in all aspects.

Introduction

mRNA Structure

Messenger RNA (mRNA) is the template that guides the synthesis of proteins and is the messenger that transmits genetic information from DNA to proteins. The structure of mature mRNA has five main parts, from 5' to 3' including 5' cap, 5' UTR, open reading frame (ORF), 3' UTR and a PolyA tail.

mRNA Cap Structure in Eukaryotes

The cap structure is critical for mRNA. Existing studies have found that the 5' cap structure can regulate mRNA splicing and maturation, and help RNA transcripts pass through selective pores in the nuclear membrane and enter the cytoplasm. In addition, the 5' cap structure protects mRNA from exonuclease degradation, cooperates with translation initiation factor proteins, recruits ribosomes, and assists ribosome binding to mRNA, enabling translation to start from AUG.

Depending on the degree of methylation, mRNAs in nature can form 3 types of caps.

• Cap 0

Guanosine is attached to the 5' end of the primary transcript by a 5'-5' pyrophosphate bond. When the 7th carbon atom of G is methylated to form m7GPPPN, the cap at this time is called Cap 0 and it exists in single cells.

• Cap 1

If the 2'-O position of the first nucleotide of the transcript is also methylated, it forms m7GPPPNm, called Cap 1, which is the majority form of cap except for unicellular organisms. The main difference between Cap 0 and Cap 1 is whether the hydroxyl group at the 2'-O position of the first nucleotide is methylated or not.

• Cap 2

If both the first and second nucleotide of the transcript are methylated at the 2'-O position, becoming m7G-PPPNmNm, it is called Cap2. Cap 2 is present in 10%-15% of eukaryotic cells.

Fig. 1 The 5′-end cap structure of eukaryotic mRNA (Ogino T,2011)

mRNA Capping Method

• Enzyme capping

This method is the most traditional. Using dsDNA as a substrate, it is transcribed to form RNA, and then subsequently modified to become mature RNA. The natural unmodified cap structure can be achieved by using vaccinia virus capping enzyme (VCE, Vaccinia capping enzyme) and dioxymethyltransferase (2'O-methyltransferase). This method can achieve almost 100% capping rate.

• Co-transcriptional capping

Cap analogs are directly used for in vitro transcription to generate capped mRNA, the process is simple, and the production capacity of mRNA vaccines and drugs can be rapidly increased.

Service Details for 5'-end Capping

Why Choose BOC Sciences

With the global biologics market becoming increasingly competitive, customer needs and market uncertainty are growing faster than ever before. BOC Sciences is committed to providing an unparalleled level of customer service to meet the needs of our customers. We believe in and are committed to the on-time, complete delivery of the products we manufacture through our flexible manufacturing solutions and proven expertise.