Taking a closer look at the behaviour of G-quadruplexes, secondary structures of DNA, to help develop next-generation drugs for the treatment of cancer. The results of studies conducted jointly by researchers of the Universities of Insubria, Milan-Bicocca and Padua, with the involvement of the National Research Council’s Institute of Photonics and Nanotechnology (CNR-Ifn), have been published in two papers in the journal Nucleic Acids Research (DOI: 10.1093/nar/gkab079 - 10.1093/nar/gkab674).
When we think of DNA, the structure that immediately comes to mind is the double helix. However, for years now it has been known that DNA can locally take on non-classical structures. One particularly relevant aspect is that these systems provide interesting opportunities for therapeutic intervention to treat many diseases, including tumours, neurodegenerative diseases, infections, and so on. Given their particular functional importance, non-classical secondary structures called G-quartets (G4s) occupy a prominent place in this setting. So far, the search for new drugs directed at these targets has not produced the desired results and this is largely due to the fact that the structure of DNA varies significantly in time and space.
The researchers analysed the conformational and nanomechanical properties of the G4s present in the promoter of a particular protooncogene responsible for several forms of cancer, combining ensemble techniques with single-molecule measurements to understand how these structures evolve over time, how their evolution is affected by the double-helix DNA matrix that surrounds them, and how they interact when they form close to one another. It has also been observed that the presence of sequences capable of forming G4s in a stretch of DNA promotes the nanomechanical denaturation of the double helix in this stretch, and hence initiates gene expression. Since the proteins involved in DNA transcription, the event that initiates protein synthesis, work by exerting forces and twists on promoters in order to induce local denaturation, the information collected constitutes a high-resolution "snapshot" of the chosen target. Finally, it was possible to follow how and how fast these sequences fold. This information will help to develop a new generation of drugs that are able to control oncoprotein production in cancer patients.
“This is a partnership between geographically-distant subjects, who are involved in a sort of delocalised laboratory and are able to create innovative non-commercially-available instruments and apply them to the characterisation of purposely-designed biological samples. All this is possible, thanks also to the support of our University Institutions that allow and facilitate this networking," declares Dr Luca Nardo of the Department of Science and High Technology of the University of Insubria.
"The research was conducted in an interdisciplinary manner, with the equal involvement of Biophysicists and Pharmaceutical Chemists. Indeed, it is only through a close collaboration between researchers belonging to scientific communities that traditionally interact only marginally, and are willing to share complementary skills, that it is possible answer apparently unanswerable questions. In this particular case, it was necessary to carry out single-molecule measurements on DNA strands that were studied literally one by one, in order to characterise aspects that are generally hidden by ensemble measurements," explains Professor Francesco Mantegazza, of the Department of Medicine and Surgery at Milan-Bicocca University".
"The key contribution of our results is that we have strongly emphasised to the scientific community that it is essential to understand the evolution in time and space of the targets we want to reach in order to intervene in an effective and targeted way. By involving scientists with apparently different visions, our network has allowed us to respond to this need by developing innovative and versatile approaches that can now be used on a broader scale," summarises Professor Claudia Sissi of the University of Padua’s Department of Pharmaceutical Sciences.
"As head of the Laboratory of Photophysics and Biomolecules in Como, which is co-owned by the CNR and Insubria, I am extremely pleased with the important results obtained in recent years and this project in particular. I would like to thank all the young researchers who have worked in the laboratory over the years, without whose dedication and expertise the research would have been impossible," concludes Professor Maria Bondani of the CNR-Ifn.