Thursday, February 8, 2018

Small molecules set up security system to defend the genome

new studies about RNA in genetic code,Small molecules set up security system to defend the genome
via medicalexpress.com
"Thousands of short RNA molecules with diverse genetic sequences serve as security guards to identify and silence attempts to invade the genome, such as DNA inserted by viruses or parasitic elements known as transposons.

These diverse, small RNA molecules, known as Piwi-interacting RNAs (piRNAs) are produced by various animals, from insects and worms to mammals like mice and humans. In a new study published February 2 in the journal Science, researchers from the University of Chicago describe how piRNAs find foreign genetic sequences to silence them. They also show how endogenous or "self" genes that properly belong in the genome identify themselves to avoid this additional scrutiny.

"Nearly every animal has these small RNAs, and they use them as a guide to look for target sequences and silence them," said Heng-Chi Lee, PhD, assistant professor of molecular genetics and cell biology at UChicago and senior author of the new study. "Until now though, it was rather mysterious what their function was, and why there are so many with such diverse genetic sequences."

A database of suspects

RNA acts as a messenger to carry out instructions coded in DNA to produce proteins that perform essential functions in the body. In the new study, Lee and his colleagues studied piRNAs produced by cells in the reproductive system of the nematode worm, C. elegans, a classic model organism studied by scientists to understand basic biological processes.

Piwi-interacting RNAs are a type of small RNAs that associate with what's known as Argonaute machinery in cells that search for target RNA and shut it down. RNA is built with the same chains of nucleotides that mirror sequences of DNA, denoted with the same familiar A, C, G, U lettering. Some small RNAs need to match the target sequence exactly to identify them, like a security guard looking for a specific person. Others small RNAs can flag genes with a partial match, more like looking for a suspect based on a general description..."

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