New Technique to Control Protein Expression

One of the problems in modern day biomedical research is turning on/off protein expression.

In order to control in vivo protein levels, many researchers have reverted to genetically tractable organisms such as yeast and worms. In the September issue of Cell, there's a cool paper by Banaszynski et al., who developed reagents so that you can pharmacological manipulate the expression of any protein in the cell.

They take advantage of the FKBP-rapamycin-FRB system, where the addition of a drug (rapamycin) promotes the association of two proteins (FKBP and FRB). Using Yellow fluorescent protein-FKBP chimeras and error-prone PCR they screened cells (each expressing a mutant version of the FKBP chimera) by FACS analysis and isolated mutant versions of the FKBP protein that are inherently unstable but become stable in the presence of a rapamycin derivative (Shld-1).

Take home: you can fuse mutant FKBP to any protein. Your protein of interest is now stable only in the presence of Shld-1.

Step 1: Transfect cells with a plasmid encoding the fusion protein (FKBP-your favorite protein). Want to see what your protein does to cells over short periods of time? Step 2: Add Shld-1 and your favorite protein can be made. Want to get rid of your protein? Step 3: Wash out the Shld-1 and your favorite protein is degraded.

Another neat new reagent.

Ref:
Laura A. Banaszynski, Ling-chun Chen, Lystranne A. Maynard-Smith, A. G. Lisa Ooi, and Thomas J. Wandless
A Rapid, Reversible, and Tunable Method to Regulate Protein Function in Living Cells Using Synthetic Small Molecules
Cell (06) 126:995-1004