A metabolic enzyme that has been studied for more than 70 years has a hidden second function – unwinding RNA and promoting cell cycle progression – beyond its role in energy production, according to new research led by the University of Surrey.
Phosphofructokinase (PFK) is the “gatekeeper” of glycolysis, an ancient and evolutionarily conserved metabolic pathway that breaks down sugars to produce energy. In the yeast Saccharomyces cerevisiae, PFK is composed of two subunits, Pfk1 (α) and Pfk2 (β). Although both have long been understood as metabolic partners, Sally and her team discovered that Pfk2 has entirely different abilities. It binds to hundreds of messenger RNAs (mRNAs) in cells, unwinds short double-stranded RNAs in specific directions, and actively promotes the translation of genes that drive cell division.
The study, published in Nucleic Acids Research, shows that without Pfk2, yeast cells grow slower, become significantly larger, and have a harder time progressing from the G1 phase of the cell cycle to the S phase, a critical transition point when cells move toward division. Importantly, reintroducing a version of Pfk2 incapable of glycolysis abolished these defects, confirming that the enzyme’s role in cell division is independent of its metabolic function.
Phosphofructokinase has been intensively studied for its role in metabolism since the 1950s. We discovered that one of its subunits, Pfk2, also functions as an RNA regulator that helps regulate cell division. This is not about energy production. We propose that the enzyme acts as a molecular relay, sensing the energy status of the cell and using that information to decide whether to promote growth. ”
Professor Andre Gerber, corresponding author of this study, School of Biological Sciences, University of Surrey
The research team used a combination of RNA sequencing, biochemical assays (laboratory tests to study the behavior of molecules), and proteomics (large-scale analysis of proteins) to build their case. They identified more than 800 mRNAs bound by Pfk2 in living cells, many of which encode proteins involved in controlling the mitotic cell cycle, the process by which cells divide into two. Using a test that uses optical signals to track RNA strands as they are pulled apart in real time, the researchers showed that Pfk2, but not Pfk1, can unwind short double-stranded RNA molecules with a specific orientation. This function is usually associated with dedicated RNA helicase enzymes, specialized proteins whose main job is to unwind RNA.
Polysome profiling (a technique that isolates cellular contents to reveal which mRNAs are actively being made into proteins) has shown that cells lacking Pfk2 detect mRNAs for important cell cycle regulators such as the G1 cyclin CLN3 (a protein that triggers the initiation of cell division) and the spindle checkpoint protein BUB3 (a protein that ensures that chromosomes are properly segregated). It became clear that the protein was dramatically separated from the ribosome and was no longer efficiently translated into protein. Proteomics confirmed reduced levels of cell cycle proteins in Pfk2 deletion mutants (cells in which the gene encoding Pfk has been removed).
The research team proposes a “molecular relay switch” model. When cellular energy is low, PFKs adopt an enzymatically active state and focus on glycolysis. When energy is abundant, Pfk2 shifts to a less active form and enhances its ability to bind and unwind RNA, promoting translation of cell cycle genes (RNA-directed protein production) and enabling cell division. This creates a direct molecular link between a cell’s metabolic state and its proliferation decisions.
For decades, PFK has been described in every biochemistry textbook as a monofunctional enzyme that acts only on glycolysis. The discovery of this dual function of PFK opens new avenues to advance our knowledge of important cellular functions. This could, for example, lead to a better understanding of diseases involving cell cycle misregulation and lead to the development of new treatments. Additionally, this discovery raises an important question – how many more hidden functions do other enzymes have that we long to discover?”
Waleed Albifulal, lead author of the study and researcher at the University of Surrey
This research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC), Cancer Research UK, and the Engineering and Physical Sciences Research Council (EPSRC). International collaborators included teams from the Scottish Institute for Cancer Research UK, the University of Osnabrück, the University of Basel and the University of Ulm.
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Reference magazines:
Albihral, WS; others. (2026) Yeast phosphofructokinase β subunit has RNA unwinding activity and regulates cell cycle progression. DOI: 10.1093/nar/gkag184. https://academic.oup.com/nar/article/54/5/gkag184/8516055
