Macchi's lab team

Rbfox2: the key to block the development of cancer cells

On the cover, Paolo Macchi’s research group (University of Trento).

Thanks to the collaboration between the University of Trento and Washington was found a solution to block the growth of cancer cells. American biologists have turned to fellow Trento laboratory directed by Paolo Macchi for their experimental skills.

Over a century of research has illuminated the darkest depths inside human cells. Ten researchers from the universities of Trento and Washington have created an engineered protein (Rbfox2, family Rbfox) capable of binding to a particular type of nucleic acid (miR-21, item that is associated with the development of cancer cells), just like a key with its lock, and that, once inside the cancer cell, manages to inhibit development.

The study, which is the result of international collaboration between the laboratory directed by Paolo Macchi (Lab of Molecular and Cellular Neurobiology, Center for integrated biology – CIBIO, University of Trento) and directed by Gabriele Varani (Department of Chemistry, Washington University), was published in the scientific journal “Nature Chemical Biology”.

The interaction between proteins and nucleic acids (specifically RNA) – says Paolo Macchi del CIBIO – is very complex and figure out how this is done and how it is regulated to create, for example, engineered molecules with novel biological properties, for purposes not only research, but also therapeutic.

The micro-RNA (miRNA) are short sequences of RNA that regulate the activity of genes and contribute to normal cell growth. Lately they have been studied in a pathological context such as cancer. An altered miRNA expression triggers a series of events leading to a neoplastic transformation of the cell and thus the development of metastasis and poor prognosis in cancer patients.

For this Varani and his team have modified a human protein called Rbfox2, which occurs naturally in the cells and binds to microRNA. The researchers had the intention of designing a Rbfox2 protein capable of binding to a specific microRNA called miR-21, which, if present at high levels, increases expression of onco-genes promoters and a reduction of onco-genes suppressors. Scholars have speculated that if a protein as Rbfox2 was bound to miR-21, it could suppress the effects of the same miR-21 on tumor growth. They were not wrong.

Gabriele Varani's research group (University of Washington)
Gabriele Varani’s research group (University of Washington)

However, in order for this process to succeed, the protein must bind to microRNA miR-21 and no one else. Fortunately, all the molecules of RNA, including microRNAs, have an inherent property that gives them special feature: consist of a chain of chemical “letters”, each with a unique sequence. To date, no other research group had ever successfully altered a protein to make it bind to a specific microRNAs. Researchers at the University of Washington have relied on high-quality data about protein structure Rbfox2 to understand, at the level of individual atoms, as it binds to its natural sequence of letters of the RNA segment.

Then have predicted how the sequence of Rbfox2 would change to attach instead to miR-21. So, altering only four carefully selected amino acids, Rbfox2 it is attached to miR-21, preventing the microRNA to send his message to promote tumors.

The researchers also engineered a second protein that should erase any miR-21 from cells. They did it with the insertion of the Rbfox2 regions that are tied to miR-21 on a separate protein called Dicer. Dicer normally separates the RNA into smaller pieces and generates functional microRNAs. Surprisingly the Rbfox2 hybrid protein-Dicer showed a particular inclination to cut the miR-21 until you delete it.

Varani and his team believe that Rbfox2 could be redesigned to attach even to microRNA other than miR-21. There are thousands of microRNA to choose from, and many are involved in diseases. The key to realizing this potential lies in the streamline and automate the accurate methods that the team used to model interactions at the atomic level of Rbfox2 with RNA. Not only could be useful lab tools to investigate microRNA functions, but, over time, would form the basis of new therapies for the treatment of diseases.

Macchi reports that colleagues from the University of Washington, who have a chemical-structural approach to the life sciences, have turned to the biologists of the CIBIO experimental for their expertise on the cells.

The work is important because it emphasizes once again the value and application of basic research. Basic research has allowed to know the structure of the regions of proteins involved in the interaction with nucleic acids, as well as discovering miRNAs and their involvement in both physiological and pathological processes. Having put together and successfully knowledge and skills of our research groups belonging to different fields of biology has been challenging and extremely interesting. This is the second collaborative work published in international journals within a few months by our two groups.

The article was published in the scientific journal Nature Chemical Biology with the title “Targeted inhibition of oncogenic miR-21 maturation with designed RNA-binding proteins”. The authors are ten. For the University of Washington: Yu Chen, Fan Yang, Tom Pavelitz, Wen Yang, Katherine Godin, Matthew Walker and Suxin Zheng with Lab Manager Gabriele Varani, while authors belonging to the University of Trento are Lorena Zubovic and Paolo Macchi, head of Lab of Molecular and Cellular Neurobiology.

The work was supported by the American Institute of health and the University of Trento (biotechnology).