For decades, biologists operated on a clean assumption: the nucleus handles genes, and the mitochondria handle energy. Two compartments, two jobs, a tidy division of cellular labour.
That assumption has just been overturned.
A landmark study published on March 6, 2026 in *Nature Communications* has revealed that **over 200 metabolic enzymes** — the molecules typically responsible for producing cellular energy inside mitochondria — are also found operating directly inside the cell nucleus, physically attached to DNA.
The discovery, led by Dr. Sara Sdelci and her team at the Centre for Genomic Regulation (CRG) in Barcelona, redraws the map of the human cell — and opens an entirely new front in the study of cancer.
**What they found**
Using a technique called 'native chromatome profiling', the researchers were able to identify all proteins associated with human DNA across a range of tissues. The metabolic enzymes they found weren't there in small numbers or by accident — they were present in large quantities, in consistent patterns, deeply integrated with the chromosome.
They weren't hitchhikers. They appeared to belong.
What's more: the pattern wasn't the same everywhere. Different cell types showed different combinations of nuclear metabolic enzymes — a unique 'nuclear metabolic fingerprint' for each tissue. And when the team analysed cancer cells, those fingerprints diverged further still: breast cancer cells showed strikingly different nuclear enzyme profiles to lung cancer cells, and both differed from healthy tissue.
For the first time, cancer can be characterised not just by what genes it has mutated, but by the metabolic signature it writes directly onto DNA.
**Why it matters**
The implications are wide-ranging.
Some of the enzymes gathered specifically around sites of DNA damage — suggesting they play an active role in **DNA repair**. This is potentially critical: many current chemotherapy drugs work by damaging DNA in cancer cells. If those same cells have metabolic enzymes positioned to repair that damage, it may help explain why some cancers become resistant to treatment.
'These findings reveal an unexpected interplay between metabolism and genome regulation,' said Dr. Sdelci. 'The nuclear metabolic fingerprints we identified may help us better understand how cancer cells grow, adapt, and resist therapy.'
The research also opens the door to a new category of biomarkers — signatures that could allow doctors to identify cancer type, predict treatment response, or track disease progression from a tissue sample.
**The wider picture**
This is fundamental biology — the kind of discovery that reshapes the way scientists think about how cells work. It means that the energy-processing machinery of the cell is not just in the mitochondria. It is also in the control room, touching the genome itself, participating in the regulation of gene expression in ways that weren't previously understood.
'We have been studying metabolism and gene regulation as separate disciplines,' one researcher noted. 'They are, in fact, in constant conversation.'
For cancer research, the timing is significant. Immunotherapy has transformed outcomes for many cancers. Targeted therapy has made others manageable. But there are still cancers that are stubbornly resistant to every available approach.
A new lens — nuclear metabolism, the fingerprints cancer leaves on its own DNA — may be exactly what's needed to find the next breakthrough.
Hundreds of enzymes, hiding in plain sight inside the nucleus, waiting to be found. 🔬
*Sources: Nature Communications (March 6, 2026) · Centre for Genomic Regulation, Barcelona · SciTech Daily · EurekAlert · ScienceDaily*
