A team of Seoul National University scientists discovered a previously unknown step in the process of producing a type of RNA molecule.

The team, led by professor Kim V-narry of Seoul National University who is a well-known name in biochemical circles, discovered a new step in the process of producing a specific type of microRNA known as let-7. The findings were published in the online edition of the biological journal The Cell.

In 2008 she was awarded the L’Oreal-UNESCO Women in Science Award, and was selected as one of the 15 Asian scientists to watch by the Singapore-based science and technology magazine Asian Scientist.

A microRNA molecule is a small chain of RNA, or ribonucleic acid, that regulates the expression of genes.

The microRNA let-7 is involved in a wide range of cellular processes ranging from cell division and growth to cell death.

In addition, recent research suggests that let-7 plays an important role in suppressing the expression of a number of genes involved in cancer.

The team showed that a group of enzymes known as TUT7, TUT4 and TUT2 mark the precursor of let-7 by adding a single nucleotide -― uridine ― to enable an enzyme called Dicer to recognize it.

The let-7 microRNA production begins with the transcription of the relevant gene which results in a single-stranded RNA. As distant parts of the RNA are complimentary, the molecule folds in on itself forming a hairpin structure.

In this structure, the parts of the molecule with matching parts line up to form a double-stranded section. The segment between them forms a small loop to create a shape resembling a hairpin.

The structure is then cut by the Drosha enzyme. The resulting structure is again cut by the Dicer enzyme resulting in a double-stranded RNA molecule without the loop.

However, researchers had found that the hairpin structure in its initial form was recognized by the Dicer enzyme at a low efficiency.

By Choi He-suk (cheesuk@heraldcorp.com)