Amazing stuff!
"Viruses plague bacteria as well as people, and some bacteria deploy ... molecular mechanism to defend themselves, two studies published in Science this month reveal. The bacteria conjure up an entirely new gene that isn’t normally in their repertoire. This gene, dubbed neo by both groups that unearthed it, then spawns a protein that stymies the viral invaders. ...
To assemble their new gene, the studies show, the bacteria exploit enzymes called reverse transcriptases, which invert a key cellular mechanism. Cells usually start with information encoded in a gene’s DNA to make RNA molecules, such as the messenger RNAs (mRNAs) that carry the instructions for synthesizing a protein. But reverse transcriptases can flip the process around and produce DNA versions of RNA molecules. Discovered in tumor-causing viruses, the enzymes also allow HIV to commandeer human cells. However, many bacteria also make reverse transcriptases, and the new work reveals how at least one kind of bacterium uses them to turn the tables on the viruses known as phages. ..."
"In a genetic sleight of hand used to ward off invading viruses, certain bacteria can assemble a gene to make an antiviral protein, two groups publishing in Science this month have shown. The unprecedented defensive maneuver ... The findings offer the latest challenge to the misperception that genetic information flows only one way—from DNA to RNA to proteins—and raise the possibility that similar cryptic genes lurk in other organisms, even humans. ..."
From the abstract:
"Reverse transcription has frequently been co-opted for cellular functions and in prokaryotes is associated with protection against viral infection, but the underlying mechanisms of defense are generally unknown. Here, we show that in the DRT2 defense system the reverse transcriptase binds a neighboring pseudoknotted noncoding RNA. Upon bacteriophage infection, a template region of this RNA is reverse transcribed into an array of tandem repeats that reconstitute a promoter and open reading frame, allowing expression of a toxic repetitive protein and an abortive infection response. Biochemical reconstitution of this activity and cryogenic electron microscopy provide a molecular basis for repeat synthesis. Gene synthesis from a noncoding RNA is a new mode of genetic regulation in prokaryotes."
Bacteria use ‘crazy molecular mechanism’ to fight viruses "Made-to-order gene could be so toxic that cells only assemble it in emergencies"
Phage-triggered reverse transcription assembles a toxic repetitive gene from a noncoding RNA (no public access)
Some bacteria (orange ball) defend themselves against phages, by assembling a gene not in their normal genome
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