A New Technique Improves the Study of Proteins
by Quynh Anh Nguyen
Recent advances made at Stanford UniversityÕs Departments of Chemistry and Chemical and Systems Biology will now allow scientists to control the function of a protein more rapidly through the administration of small molecules. In a paper published in the September 8th issue of Cell, Dr. Thomas Wandless and his team describe a revolutionary technique that allows researchers to control the stability of specific proteins in mammalian cells. This breakthrough has the potential to make the study of proteins dramatically better, faster, and more efficient.
Proteins and Their Basic Job Description
Proteins are long strands of amino acids that control almost every cellular function, including the synthesis and destruction of tissues, cell signaling, cell cycle control and regulation, and the immune response. Sections of DNA called genes contain the information that codes for specific proteins. This information is first transcribed into a messenger RNA (mRNA) molecule, which is then translated, or decoded, to produce the amino acid sequence. These chains of amino acids then fold into the complex structure of a functional protein. Traditional Methods of Studying Proteins
Researchers often try to decipher the role a protein plays by knocking out or knocking down the expression of the protein product and observing the resulting effects. Traditionally, this is done by making part of the gene that codes for a specific protein inactive. Unfortunately, any protein created prior to inactivation of the gene remains in the test subjectÕs system. Therefore, researchers must waitÑsometimes for several daysÑfor the protein to exit the system before continuing onto the next step in their research protocol. Another disadvantage to this technique is that it may not be successful in completely inhibiting the production of a particular protein.
A New On/Off Switch
Dr. Thomas Wandless and his research team have identified a molecule that acts as a switch to control protein function. In their experiment, a destabilizing domain was fused to the end of a protein of interest by manipulating the DNA that codes for the protein. When the modified DNA sequence was translated into a protein, the destabilizing domain was expressed as an attachment of the protein. Proteins expressed in this manner were found to be quickly degraded and completely inactivated. Next, the research team synthesized a protein dubbed Shield-1 (Shld1) that inhibited degradation by binding to the destabilizing domain. The result was that scientists were able to control the presence of specific proteins more easily and reliably by controlling the presence of Shld1. In the presence of Shld1, the protein can be stably expressed, while in the absence of Shld1 the protein is quickly degraded. Under this new technique, the waiting time for the protein to degrade is reduced to an average of four hours.
Prospects for New Findings
This finding has a significant impact on many types of research. With this technique, scientists can more accurately study the effects of a protein at a particular instant in a cellÕs life. After employing the method with several proteins, Wandless reported, ÒWe have not yet seen any cases where it doesnÕt work.Ó This new method can be used in a variety of protein settings to aid with research in areas such as metabolism and immune response, where reactions generally happen quickly.
The method also provides three great features of flexibility to experiments. First, Shield-1 has a high bioavailability and can be administered directly to the cell or the food of certain test subjects. Second, the technique is reversible: when Shield-1 is removed, the target protein is degraded and inactivated. Finally, the level of protein expression can be tuned according to the dosage of the administered Shield-1 ligand. The ease and flexibility with which this new technology can be applied makes it a useful tool for studying protein function. In fact, this approach has already been employed in experiments at several Stanford and non-Stanford labs using specimens including human cells.
Currently the method is limited only to mammalian cells, but WandlessÕ team continues to study the different capabilities of this new technology and is currently applying their research to yeast cells which are important for genetic studies.. ÒIÔd be very surprised if we werenÕt successful,Ó asserts Wandless.