Michigan Cancer Research Fund                                                                                            American Cancer Society
   
test tube  
   


Research Project Description and Objectives from Kurt Januszyk, PhD, MCRF 2010 Fellow
Dr. Kurt Januszyk

Project Name: Investigations into How the Exosome Recognizes and Degrades RNA


My research focuses on how a group of proteins called the RNA exosome recognizes and cuts RNA messages that cause cancer. 

We know that the exosome destroys RNA messages that encode proteins by cutting them into small pieces of RNA, functioning like scissors.  For unknown reasons, the exosome does not cut up RNA messages that encode cancer-causing proteins.  An understanding of how the exosome recognizes and cuts RNA messages will give insight into how proteins that cause cancer are produced.

In my research, I will:

  1. Study the function of the exosome. To do this, I need to isolate an exosome.  Since the exosome contains many different proteins, I first need to generate the different proteins of the exosome from cells. Afterward, I will purify each protein and assemble them into the exosome complex.
  2. Once I obtain a pure exosome, I will use a process called x-ray crystallography on it.  X-ray crystallography is a technique that can reveal the structure and function of molecules.  Using this technique, I hope to obtain a molecular snapshot of the exosome caught in the act of cutting RNA.
  3. This snapshot will help me determine which component of the exosome is the ‘motor’ that performs the cutting.  However, additional biochemical studies will be employed to corroborate what component is the ‘motor.’ 

Summer 2011 Update
In the coming months, I will be working to find out how to crystallize the RNA exosome, and will then take a ‘snapshot’ of the exosome crystals via x-ray diffraction to determine how it cuts RNA.

Summer 2012 Update
Most of my efforts have focused on refining conditions to crystallize the RNA exosome for structural characterization.  Additional biochemical work has successfully located the ‘motor’ component of the RNA exosome and these studies are providing insight into how RNA messages are fed into the motor and cut.

Summer 2013 Update
Biochemical and structural research findings of how the exosome recognizes and cuts RNA are now being validated for their physiological relevance.  This work is now being prepared for publication.

Summer 2014 Update

My research funded by the MCRF and ACS focused on an assembly of proteins collectively termed the
RNA exosome. The function of the RNA exosome is to destroy RNA messages that encode for proteins
and thereby regulate the expression of proteins. In order to cut the RNA messages, the RNA
exosome contains two different regions that work like 'molecular scissors'. The mechanism of
this process is an area of interest within carcinogenesis, because the exosome does not cut up
RNA messages that encode cancer-causing proteins; moreover, the 'molecular scissors' are mutated
in different forms of cancer.

To learn the cutting mechanism of the RNA exosome, we used x-ray crystallography to take a
snapshot of the RNA exosome caught in the act of cutting RNA. Through this work, we found that
the exosome looks like a donut with the two aforementioned molecular scissors located either on
top or below the donut. The RNA either threads through the length of the donut to go into the
bottom pair of scissors, or traverses the top of the donut to go into the top pair of scissors.
These findings were validated biochemically and are conserved from lower eukaryotes to human RNA
exosomes. Importantly, based on this work, we determined that a sub-set of the RNA exosome
mutations detected in cancer would disrupt the ability of the RNA exosome to cut RNA messages.

These findings were publised in Nature International Weekly Journal of Science in July 2014. I continue to work as a Research Fellow at Sloan-Kettering Institute for Research.