Oxford Improves Production Method for Interfering RNA

Researchers at Oxford University’s Department of Biochemistry have developed methods for making RNA duplexes and single-stranded RNAs of desired length and sequence. This exciting technology is most applicable to commercial RNA providers and companies with large in-house requirements for RNA molecules as it will greatly increase cost-effectiveness.

Small interfering ribonucleic acids (siRNAs) are powerful laboratory tools for directed post- transcriptional gene expression knockdown and inhibition of viral propagation. For siRNA to be active, it is important that the overhang in the antisense strand is complementary to the target messenger RNA. Exogenous siRNA is frequently used in RNAi studies using chemically synthesised RNA oligonucleotides to identify reagents with optimal activity.

Chemical synthesis of RNAs is relatively straightforward, but can be prohibitively expensive. Intracellular expression provides a source of continuous production of RNA in the cell, but it offers little control over the quantity of the expressed RNA and the sequence length. In vitro transcription is relatively cheap and offers a good approach to synthesis of large quantities of RNA. Unfortunately, in vitro transcription is limited by specific sequence requirements that greatly reduce the number of potential target sites for siRNA selection. Highly efficient promoters cannot be used, due to the leader sequence being transcribed and incorporated into the siRNA, leading to a further disadvantage. The inclusion of these leader sequences ultimately prevents the siRNA from efficiently functioning in RNA interference.

The methods of the Oxford invention rely on cleavage of primary single-stranded RNAs at a defined position in order to generate RNA strands of a required length and sequence. If it is desired to produce an RNA duplex, then two such RNA strands having complementary sequence, over at least a portion of their length, may be synthesised and then annealed to form an RNA duplex.

Isis Innovation, Oxford University’s technology transfer company, has filed a patent on this exciting technology and is actively seeking partners to commercialise it. Incorporated into the production process of commercial providers of RNA, the Oxford technology would provide huge potential benefits, greatly reducing the cost per nucleotide for RNA products.