Scientists publish largest catalog of how human cells read DNA

An international team of scientists has published what they describe as the most comprehensive catalog to date of how human cells interpret their genetic instructions, mapping the DNA-binding preferences of hundreds of transcription factors and revealing how chemical modifications reshape those interactions.

The Codebook

The research, led by Timothy Hughes at the University of Toronto and published in Nature on August 4, combined five experimental platforms with computational analyses to characterize 332 transcription factors — proteins that bind specific DNA sequences to control when and where genes are active. The team performed more than 4,800 experiments and identified DNA-binding motifs for 177 transcription factors that were previously poorly characterized, adding around 130 distinct motifs to the known vocabulary of human gene regulation.phys+2

The result is a resource the researchers call the "Codebook." With its completion, 1,421 human transcription factors are now associated with a DNA-binding motif. The human genome contains roughly 1,600 transcription factors in total, meaning the catalog now covers the vast majority of these regulatory proteins.biorxiv+1

"Our genomes contain the instructions for life, but understanding how cells actually read those instructions has remained one of biology's major challenges," said Bart Deplancke of EPFL, a co-corresponding author on the study. "This work brings us much closer to a complete dictionary of the proteins that control gene expression."miragenews+1

A Chemical Layer on Top of DNA

In a companion paper published in Nature Communications, Deplancke's team introduced meSMiLE-seq, a microfluidic method that simultaneously compares how transcription factors bind methylated and unmethylated DNA. The researchers studied 114 transcription factors and obtained binding models for 48. Of those, 14 showed greater affinity for methylated DNA or recognized alternative methylation-dependent motifs, while 13 showed reduced binding to methylated sequences.biorxiv+2

"DNA methylation does not simply switch genes on or off," said Antoni Gralak, the study's first author. "It changes how the genome is interpreted. Our work shows that many transcription factors effectively read an additional layer of information that sits on top of the DNA sequence."phys

Implications for Disease Research

Together, the two studies offer a more complete picture of gene regulation. The Codebook establishes where transcription factors can bind based on DNA sequence alone, while the meSMiLE-seq work shows how chemical marks further modify that recognition. The collaboration drew on more than two dozen institutions across North America, Europe, and Russia.miragenews

According to the University of Toronto, the findings illuminate tens of thousands of previously unknown binding sites throughout the human genome. Deplancke said the work could improve how scientists interpret genetic variants associated with disease and help explain why identical DNA sequences behave differently across cell types — questions central to understanding development, aging, and cancer.actu.epfl+2