Spliceozom can be thought of as a film editing machine that selectively cuts out unusable material (introns in this case) from the original film and sends the cleaned version of the film to the director.
The scientific journal NATURE has just published the discovery of a research team led by Dalibor Blažek, which describes a hitherto unknown mechanism regulating RNA splicing, which is an absolutely essential process for controlling gene expression. RNA splicing is carried out by the spliceosome – a cellular shearing machine whose task is to remove “junk” RNA from the newly formed RNA. Scientists have shown that a protein called CDK11 plays a central role in the assembly and activation of the spliceosome and in the regulation of splicing. In addition, Blažek’s research team showed that the anti-tumor molecule OTS964, which has the ability to exclusively target CDK11, affects the splicing process. The effect of CDK11 on spliceosome activation was unknown until now. The research results of Dalibor Blažek and his colleagues open new paths in the research of splicing and gene expression. Splicing control through CDK11 inhibition may also lead to therapeutic applications in the future.
Scientists had previously suspected that CDK11 might play a role in RNA splicing, but the exact mechanism was unknown. One reason for this unknown was the lack of compounds capable of manipulating CDK11 activity exclusively. Jason Sheltzer’s landmark 2019 discovery showed that a molecule called OTS964 inhibits CDK11 while killing cancer cells by inhibiting CDK11 activity. However, what exactly CDK11 does in cells was not known. The discovery of OTS964 caught the attention of Dalibor Blažek, whose laboratory has been studying the CDK11 kinase for many years.
Blažk’s research team first wanted to find out whether the inhibitor OTS964 targets only CDK11, or whether it also affects other CDK11-like proteins, so-called kinases, in cells. The team tested OTS964 in combination with 412 human kinases and performed additional experiments and found that OTS964 indeed only targets CDK11. Such a strong match between a kinase and an inhibitor is very rare because most inhibitors also act on other kinases and inadvertently shut them down. An inhibitor can be thought of as a switch that can turn off a kinase, thereby affecting its activity. Kinase inhibitors block the activity of specific kinases and are often used to stop the growth of tumor cells. For the successful identification and clinical approval of antitumor inhibitors, it is extremely important to know exactly which cellular mechanism is controlled by the kinase. The finding that OTS964 exclusively targets CDK11 and affects splicing therefore opens new avenues of research. This perfect match also made OTS964 an excellent tool to investigate what role CDK11 plays during the splicing process and in the cell in general.
The spliceosome plays a key role during the splicing process. Spliceozom can be thought of as a film editing machine that selectively cuts out unusable material (introns in this case) from the original film and sends the cleaned version of the film to the director. During splicing, unnecessary parts of the RNA (introns) are removed from the newly created RNA. This process is controlled by the spliceosome, which undergoes precisely regulated assembly. “We demonstrated the central role of CDK11 in the assembly of the spliceosome and in the regulation of splicing, and also that the molecule OTS964 acts as a CDK11 inhibitor, which suppresses the activation of the spliceosome and thus affects the entire splicing process,” explains Dalibor Blažek.
Activation of the spliceosome is crucial for the regulation of splicing. However, the activation mechanism is very complex and scientists still do not fully understand it. “We have characterized a new mechanism and discovered a new tool that can manipulate this mechanism. Regulation of splicing by CDK11 could also have therapeutic potential and opens the door for future studies of CDK11 and other roles that this kinase could play in RNA splicing and gene expression,” concludes Blažek.
This study is an example of meaningful interdisciplinary collaboration between colleagues from several institutes and fields. The experimental part of the study was led by the first authors Milan Hluchý and Pavla Gajdušková from the research group of Dalibor Blažek, who performed genomic, biochemical and molecular biological experiments with the help of Michal Rájecký and Zuzana Slabá. Bioinformatic analyzes of the genomic data were performed by the laboratories of Caroline Friedel (LMU Munich), Jernej Ule (Crick Institute, London) and Igor Ruiz de los Mozos (Crick Institute/University of Navarre). The laboratories of Kamil Paruch (Department of Chemistry, Masaryk University) and Stefan Knapp (Goethe University, Frankfurt am Main) performed the chemical-biological characterization of OTS964, and the research group of Zbyňka Zdráhal (CEITEC, Masaryk University) helped with the analyzes of the proteomic data. The work was financed by a standard GAČR grant, GAMU grants and the CEITEC Institute of Masaryk University.