Just Another Protein Interaction Model

Just Another Protein Interaction Model

Andrea Pichler and colleagues from Mallinkrodt Institute of Radiology describe the generation of a transgenic Gal4-luc reporter mouse (G4F) that expresses the Firefly luciferase (from pGL3, Promega) under the regulatory control of a concatenated (5x) Gal4 promoter. The Gal4-luc strain, would allow noninvasive bioluminescence imaging of protein-protein interaction in vivo, a feature of real interest since traditional biochemical techniques often miss the detection of weak and transient interactions and, more often, return false positives. So, how does it work?

Protein interaction studies with Gal4-luc reporter mouse

Actually I'm quite frightened about this model: let I want to know whether protein X (bait) and Y (from library) interact in vivo. In order to detect XY interaction with the G4F mouse, I need to tag X with Gal4BD (get a X-Gal4BD expression vector) and then tag Y with VP16 (get a Y-VP16 expression vector). Then I have to make two more transgenics (and deal about positional effects) and, once I get them, backcrossing them in the G4F background and, like a juggler, breed and genotype three markers together. Three years are enough? Of course, an alternative would be to make transfections in vivo (i.e. with hydrodynamic somatic gene transfer or viral delivery) but even this job will need some validation (i.e. not seeing an interaction means that the interaction did not appear or it’s a false negative due to problems in vector delivery. In conclusion protein-protein interaction is so hot and so hard matter, and my feelings are similar to those expressed for the Tango Assay:

There is a trend to interpret complex systems with complex conceptual design in today's molecular pharmacology. For sure this is geeky, funny, and sexy for mind, so it is worth being mentioned in Reportergene. Nevertheless I don't know whether this would be useful also to understand our inner biology. Managing three transgenes (also transiently) is not a joke. Using strong promoter to express receptors and cognate ones is unphysiological and very, very naive.


A. Pichler, J. L. Prior, G. D. Luker, D. Piwnica-Worms (2008). Generation of a highly inducible Gal4-Fluc universal reporter mouse for in vivo bioluminescence imaging Proceedings of the National Academy of Sciences, 105 (41), 15932-15937 DOI: 10.1073/pnas.0801075105