Surprising discovery finds proteins can be assembled without genetic instructions ~ Sends scientists back to drawing board

Excerpt from news.bioscholar.com

A study has shown for the first time that the building blocks

of proteins can be assembled without instructions from DNA or messenger

RNA (mRNA).

A protein, Rqc2, was found playing a role similar to that of mRNA and

specifying which amino acids, the building blocks of proteins, to be

added in cell mechanism.

“In this case, we have a protein playing a role normally filled by

mRNA,” said Adam Frost, assistant professor at University of California,

San Francisco.

“This surprising discovery reflects how incomplete our understanding

of biology is,” said first author Peter Shen, a postdoctoral fellow in

biochemistry at the University of Utah in the US.

The researchers added that the findings have implications for new

therapies to treat neurodegenerative diseases such as Alzheimer’s,

Amyotrophic lateral sclerosis (ALS) or Huntington’s.

The researchers described that ribosomes are machines on a protein

assembly line, linking together amino acids in an order specified by the

genetic code.

When something goes wrong, the ribosome is generally

disassembled, the blueprint is discarded and the partly made protein is

recycled.

The new study, however, revealed that before the incomplete protein

is recycled, Rqc2 can prompt the ribosomes to add just two amino acids

(of a total of 20) – alanine and threonine – over and over, and in any

order.

The nonsensical sequence likely serves specific purposes. The code

could signal that the partial protein must be destroyed, or it could be

part of a test to see whether the ribosome is working properly, the

researchers noted.

For the study, they fine-tuned a technique called cryo-electron

microscopy to flash freeze, and then visualse, the quality control

machinery in cells in action.

The findings appeared in the journal Science.

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Surprising discovery finds proteins can be assembled without genetic instructions ~ Sends scientists back to drawing board