What are microRNAs?

Why in the news?

In 2018, a team found through in vitro studies that when breast cancer cell lines were treated with progesterone, two genes — SGK1 and NDRG1 — were produced in excess amounts (overexpressed). They also found that the expression of a few microRNAs was reduced (down regulated) in response to the hormone treatment.

• Two particular microRNAs that were down regulated were found to also regulate the expression of the SGK1 gene.

• A recent study has found that treatment of breast cancer cells with progesterone results in a down­regulation of a long non­coding linc RNA known as the Down Syndrome Cell Adhesion Molecule (DSCAM­AS1).

• As with progesterone therapy, the researcher found that with silencing of DSCAM- AS1 expression, the ability of breast cancer cells to invade and migrate is slowed down.

• In breast cancer patients, the amount of DSCAM­AS1 present is elevated. The team also found that DSCAM­AS1 behaves like a sponge and depletes the availability of another non-coding microRNA called the miR­130a.

• And the level of estrogen receptor in breast cancer cells is increased, which serves as an indicator to begin hormonal therapy. (Source: The Hindu)

What are MicroRNAs (miRNAs)?

• MicroRNAs (miRNAs) are small noncoding RNAs that function as major players of posttranscriptional gene regulation in diverse species.

• It is the name of a family of molecules that helps cells control the kinds and amounts of proteins they make. That is, cells use microRNA to help control gene expression. Gene expression refers to whether a particular gene is making too much, too little or the normal amount of its protein at a particular time.

• Molecules of microRNA are found in cells and in the bloodstream.

• Along with genes that encode the information for making proteins, cells have genes that encode the information for making microRNA.

• In cancer cells, microRNA genes can be damaged by mutations. A mutation in a microRNA gene can leave the cell without that particular microRNA or reduce it to a low level in the cell.

• Abnormally low levels of a microRNA can lead to overexpression of genes that that microRNA regulates, and that can lead to cancer development and progression.