The protein DNase1 is one of the oldest biological agents in history: It has been on the market since 1958 and is now used, among other things, to treat cystic fibrosis. However, it takes considerable effort to produce it in immortalized hamster cells. This process is also costly. It would be far more cost-effective to produce it with undemanding yeast cells. A team under Dr. Markus Napirei in the Department of Anatomy and Molecular Embryology at Ruhr University Bochum, led by Professor Beate Brand-Saberi, has been able to achieve this for the first time. “This is the result of years of work, and could lay the groundwork for the manufacture of human DNase1 in yeast as a biological agent,” says the researcher. The work was published in the journal PLOS One on April 29, 2025.

The yeast fungus Pichia pastoris is a popular aid in manufacturing therapeutically effective biological agents. The genetic information of the desired protein is implanted into the yeast cells with an electrical impulse via an artificial, lab-produced DNA molecule. The yeast cells then stably integrate this molecule into their genome, read it, and release the protein coded therein. “The advantages of yeast over mammalian cells are cost-effective culture conditions, a high rate of reproduction without the need to immortalize cells, and lower susceptibility to pathogens,” explains Napirei.

In his doctoral thesis, Jan-Ole Krischek, supervised by Napirei and Professor Hans Georg Mannherz, he was able to express human DNase1 in Pichia pastoris, clean it, and characterize it for the first time. The researchers were surprised that the yeast produced considerably less human DNase1 than the mouse DNase1 that had been used as a guide, although both proteins share 82 percent of their primary structure. “This is partly due to the specific folding behaviors of the two proteins,” says Napirei. With regard to biochemical and functional characteristics, mouse DNase1 somehow serves as the model for the pharmacologically adapted isoforms of human DNase1 that are currently in development.

DNase1 is a protein that occurs in bodily secretions and fluids. Its purpose is to degrade cell-free DNA that the body can then dispose of or recycle. The body can release DNA from its own cells and microorganisms at various locations which, under certain circumstances, induces symptoms of illness, such as those occurring during cystic fibrosis. This disease results in tough bronchial mucus that also contains DNA. The human enzyme DNase1 has been produced from ovary epithelial cells in hamsters and marketed since 1993. The inhaled DNase1 liquifies the DNA-laden and thus viscous bronchial mucus, which makes it easier to cough up.

DNase1 could potentially be used in other pathological processes as well. This endonuclease is an important factor in removal of neutrophil extracellular traps (NETs) that serve primarily to immobilize bacterial pathogens. In the event of sepsis but also a severe infection with SARS-CoV-2, there is a pathologically increased formation of NETs and microthrombi that contain high levels of NET components. “It could be useful to use DNase1 to better dissolve these microthrombi that contain DNA,” explains Napirei. Another example is the use of DNase1 to dissolve the thrombosis of a cerebral artery in the case of ischemic strokes, which clinical studies are currently exploring.