Researchers at Kyoto University and RIKEN have uncovered a hidden regulatory system in the human genome that selectively silences less efficient genetic instructions. The study, published April 9, reveals that cells can distinguish between genetic messages that appear identical but perform differently.
For decades, scientists viewed synonymous codons—different three-letter genetic sequences that code for the same amino acid—as interchangeable. This new research proves that some codons are functionally superior, while others are "non-optimal" and prone to being discarded by the cell.
The role of DHX29 in gene regulation
The research team, led by Osamu Takeuchi and Takuhiro Ito, utilized genome-wide CRISPR screening to identify the molecular machinery responsible for this process. They discovered that an RNA-binding protein named DHX29 plays the primary role in identifying these weaker genetic messages.
Using cryo-electron microscopy, the team observed DHX29 interacting directly with the 80S ribosome, the cellular structure responsible for protein synthesis. The protein specifically targets ribosomes currently translating non-optimal codons.
Once DHX29 identifies these weaker sequences, it recruits a protein complex known as GIGYF2•4EHP. This complex suppresses the mRNA, effectively preventing the production of inefficient protein chains.
"Together, these findings reveal a direct molecular link between synonymous codon choice and the control of gene expression in human cells," said co-corresponding author Masanori Yoshinaga.
This discovery challenges long-held assumptions about how cells manage their genetic output. By proving that codon choice directly influences gene expression, the researchers have identified a new layer of biological control that could impact everything from cellular differentiation to the development of cancer.
"We have long been fascinated by how cells interpret the hidden layer of information embedded within the genetic code," said team leader Osamu Takeuchi. "Discovering the molecular factor that allows human cells to read and respond to this hidden code has been particularly rewarding."
The research team plans to continue their investigation into how the DHX29 mechanism functions under various health conditions. They believe understanding this quality control system could eventually provide insights into how cells maintain their internal balance and protect themselves from inefficient genetic instructions.
