🧬 Life Uses 4 DNA Letters. Scientists Just Made 8 Work.

Every known organism on Earth writes its genetic instructions using the same four DNA letters: A, T, C and G.

Scientists have now shown that one of biology’s most fundamental molecular machines can read an alphabet containing eight.

Researchers tested E. coli RNA polymerase — the enzyme that reads DNA and turns its information into RNA — with synthetic DNA containing four additional chemical letters known as P, Z, B and S. Remarkably, the enzyme successfully recognized and transcribed the artificial base pairs using much of the same molecular machinery it employs for natural DNA.

Using cryo-electron microscopy at resolutions down to about 2.4 ångströms, the team could watch how the synthetic letters fit inside the polymerase. The artificial pairs adopted almost the same geometry as ordinary Watson–Crick DNA pairs, allowing the enzyme’s catalytic machinery to close around them and continue transcription. Researchers also engineered a modified version of one synthetic letter to reduce copying errors.

The implications are potentially enormous. A larger genetic alphabet could eventually produce RNA molecules with chemical capabilities unavailable to natural biology and might help scientists design new diagnostics, drugs and engineered biological systems. Expanded genetic alphabets have already been used experimentally to create molecules that recognize cancer cells.

But there is an important boundary: scientists have not created an eight-letter living organism here. The experiment demonstrates transcription by bacterial RNA polymerase; reliably replicating a full eight-letter genome and translating that expanded information into proteins inside living cells remain much harder problems.

For four billion years, life on Earth has been writing with four letters.

Apparently, biology’s machinery can read a bigger alphabet than evolution ever gave it.

#Genetics #DNA #SyntheticBiology #Biotechnology #RNA #Science

Primary paper — Nature Communications⁠

🧬 An AI Just Made a Biological Discovery

Not summarized a paper.
Not predicted a protein structure.

Found something in nature that scientists apparently hadn’t noticed before.

Researchers gave Claude AI agents a relatively broad task: search enormous DNA databases for unusual reverse transcriptases — enzymes that copy RNA into DNA.

Then they mostly stepped aside.

About 950 AI agents spent 21 hours analyzing more than 200,000 enzymes, narrowing them to 3,500 candidate systems and eventually 20 especially interesting ones.

One agent noticed something strange.

Next to a reverse transcriptase gene in a bacteriophage — a virus that infects bacteria — it found a long, organized array of repeating DNA sequences.

The pattern looked oddly familiar.

It resembled the repeat architecture of CRISPR.

Claude investigated the sequence, measured the repeats, compared them with known systems and searched the scientific literature. It concluded that the combination appeared to represent a previously uncharacterized biological system.

Human scientists then took over in the laboratory.

Their initial experiments supported a key prediction: the mysterious DNA array is actually expressed into multiple short RNA molecules.

The researchers named the system ART — array-associated reverse transcriptases.

And this is where the story gets interesting.

CRISPR also contains arrays that generate short RNAs, which ultimately help make the system programmable. Several other recently discovered molecular systems with similar combinations of features can cut, copy or insert genetic material.

But an important warning: nobody yet knows what ART actually does.

This is an early preprint, not a peer-reviewed discovery, and there is currently no evidence that ART is a new gene-editing system. Experiments are still underway to determine its biological function.

The bigger story may therefore be Claude itself.

For decades, biological discovery depended partly on humans noticing something strange hidden inside enormous datasets.

Now we may have machines capable of doing the noticing.

What happens when thousands — or millions — of AI scientists start searching nature simultaneously?

#AI #Biology #CRISPR #Genetics #Biotechnology #Claude #Science

https://www.anthropic.com/news/claude-discovers-novel-enzyme-system