Stylised DNA strands

Scientists at The Scripps Research Institute have developed a new method for producing ribonucleic acid (RNA) molecules in the laboratory.

The method works for ordinary RNA and for several types of modified RNA, reports Scicasts. It has the potential to bring down dramatically the cost of producing RNA for scientific and pharmaceutical applications.

Senior investigator, Floyd Romesberg, a professor of chemistry ar TSRI, explained, “Already three companies have contacted me about licensing this technology, so it’s not just proof of principle, it’s going to be used.”

There are two conventional RNA-making methods. One uses organic chemistry reactions, and is only suited for producing short RNA strands. The other employs a natural enzyme called an RNA polymerase to transcribe RNA strands from a starting strand of DNA. The polymerase-based method broadly mimics the transcription of RNA that occurs in cells; but in an artificial, test tube environment it turns out to be very inefficient.

First author, Tingjian Chen, a postdoctoral researcher in the Romesberg Laboratory, said, “With traditional test-tube transcription, the yields of RNAs are usually not high (compared to PCR of DNA), and for the short RNAs they are even lower.”

The new method in question emerged from a research effort centring on PCR, the DNA-amplification technique. Due to the copies and the starting fragments are all in DNA form and essentially identical, the products of each cycle of synthesis can serve as the starting templates for the next cycle. In typical 15-30 cycle amplification, PCR can produce millions of copies of a DNA strand, starting from a tiny number of originals.

Chen discovered that SFM4-3 works very well at producing ordinary RNA strands. Even more importantly, he found that the artificial polymerase can power a PCR-like chain reaction, resulting in an exponential production of RNAs.

The process that is being called polymerase chain transcription (PCT) is conceptually more complex than PCR. It involves the creation, and duplication in each cycle, of hybrid strands of DNA-plus-RNA, and the removal of the DNA with DNA-chopping enzymes at the end, leaving just the amplified RNA. In addition, it also yields a quantity of the desired RNA that can be at least several orders of magnitude greater than the quantity of DNA used as a starting template for transcription.

In an example to demonstrate the method’s practical potential, Chen used it to produce a modified RNA molecule that is being investigated as a possible anticoagulant therapy. The new method would never be costly.

With the current price of producing ordinary short RNAs at 10-20 times the cost of making short DNAs, and the cost of making modified short RNAs is typically 100-200 times greater. The new method should close most of that RNA-DNA cost gap.


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