Indian scientists make a breakthrough in 'gene silencing'

Friday, 20 February 2004, 08:00 Hrs
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HYDERABAD: Scientists at a premier biotechnology research laboratory here have discovered a new approach to "gene silencing", a phenomenon that suppresses genetic expression.

This discovery has a potential to develop treatment of cancer and other diseases caused by cell proliferation, Centre for Cellular and Molecular Biology (CCMB) director Lalji Singh said Friday.

He was announcing the discovery by a 13-member team of scientists led by Utpal Bhadra and his wife Manika Pal Bhadra.

The scientists are now working to find out whether this new approach in gene silencing can delay the cell division in cancerous cells. The tests are being conducted on mice, which have 85 percent of their genes similar to humans.

When the gene expression is completely stopped, or reduced dramatically, the phenomenon is known as gene silencing. The genes in plants and animals are silenced by interfering with their activity through RNA, a relatively small molecule. The process is known as RNA interference (RNAi).

Gene silencing was first identified in plants in 1987 and a decade later in animals. The importance of RNAi in antiviral therapy and drug validation has already been illustrated.

In transgenic plants and animals, multiple copies of transgenes introduced into host genome become inactive due to such interactions. Simultaneously, even some of the host genes get silenced.

This creates a major obstacle for biotechnologists who are engaged in creating transgenic organisms with new traits of crop improvements and animal husbandry, or doctors who look forward to use gene therapy for treating diseases.

The CCMB scientists have found a way to overcome this obstacle by preventing the silencing of certain genes.

By using the chromosomes of fruit flies Drosophila, Utpal Bhadra and his team have demonstrated that gene silencing was achieved by small RNAi at specific loci during the conversion of euchromatin to heterochromatin.

Chromosomes found in the nucleus of every cell contain two parts - heterochromatin, which is located at the centre as well as at the end of the chromosome and play an important role in cell division and cell proliferation, and euchromatin, which is populated with a large number of genes.

In their paper published in the January issue of the prestigious journal "Science", the team demonstrated that disruption of RNAi interference mechanism in the living cell, blocks the formation and maintenance of heterochromatin, eventually leading to disruption of specific chromosome regions.

"Diseases coupled with cell division and cell proliferation, such as various types of cancers, appear to be controlled by heterochromatin formation and its functioning," said Manika Pal Bhadra.

"Understanding the role of RNA-I intervention in these processes, thus, might pave way to use RNAi as a possible therapy for cancers and other related diseases, which involve cell cycle controls," she added.

Source: IANS
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