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(GIST OF SCIENCE REPORTER) Jumping Genes

(AUGUST-2024)

Nature recently published a paper by researchers at the University of California, Berkeley, and the Arc Institute in the U.S. describing a new RNA-guided gene editing system.

These are genes that are able to move around within the genome.
Depending on where the mobile elements are inserted, they have the ability to reversibly alter gene expression.
Between 1948 and 1983, researchers found transposons in an array of life-forms, including bacteriophages, bacteria, plants, worms, fruit flies, mosquitos, mice, and humans. They were nicknamed jumping genes.
There are two classes of jumping genes, called class I transposons and class II transposons.
Class I transposons are also called retrotransposons because when they undergo the process of replication, they first copy their DNA into RNA
Class II transposons are DNA sequences that move from one location to another in a genome using a “cut-and-paste” mechanism.

The discovery of transposons revolutionised our understanding of genetics.
Transposons influence the effects of genes by turning ‘on’ or ‘off’ their expression using a variety of epigenetic mechanisms.
They are rightly called the tools of evolution, for their ability to rearrange the genome and introduce changes.
More than 45% of the human genome consists of transposable elements.
They also create mutations in genes and lead to diseases.

Researchers in USA found a new RNA-guided gene editing system. It builds on an older discovery, that one of the genes in the IS110 family of bacterial transposons contains the instructions for cells to make an RNA molecule with two loops.
This RNA could bind to two pieces of DNA, rather than the usual one piece, and form a bridge between them. This is a very useful ability.
The two loops of the RNA can independently bind to two separate pieces of DNA.
One of the loops identifies the target site in the genome that needs to be altered. The other loop specifies the DNA to be inserted in its place. Each loop is independently programmable, which means researchers can mix and match any target and donor DNA sequences of interest.

Bridge RNA serves as an alternative form of genome-editing. It has several advantages.
CRISPR-mediated editing sometimes leaves small bits of nucleotides added/deleted during the repair process.
DNA recombination mediated by bridge RNA on the other hand makes a clean cut, making the edit specific and tidy.
It can facilitate the addition, deletion or inversion of DNA sequences of virtually any length.