This system utilizes a mutant strain of Drosophila in which the 2 native receptors of the ab3A neuron have been deleted, this creates a nonresponsive Δab3A in which other receptors can be expressed and functionally tested.
First, we were able to recapitulate the induction of ER stress observed in mammalian systems with a mutant form of human SOD1.
Once such a system is created, a mutant strain hosting the altered network can then be evolved under controlled experimental conditions, and system-level adaptive responses can be subsequently tracked using whole-genome sequencing analyses.
To obtain a suitable test system, we generated a mutant yeast strain in which the Put1 gene, encoding the single ProDH, was replaced by a kanamycin and geneticin resistance cassette by homologous recombination.
This behavior is strikingly similar to that of the Cairns system, in which a mutant lac operon carried by an F′ plasmid regains function under selection (Cairns and Foster 1991).
In our ES and mouse model systems, a weaker mutant (RIαB) is being transcribed from only a single allele under the control of the endogenous RIα promoter and this may not be adequate to sequester all of the available C subunits.
This principle is the basis behind several conditional degradation systems in which a mutant of FKBP12 is attached to a protein of interest.
Interestingly, using COS-1 cells as a eukaryotic expression system, all mutants except for those targeting p.L34 were found to be synthesized and secreted to the cell supernatant, from which they could be purified for further experiments [31],[32].
Unfortunately, the DAP selection system requires working in a mutant strain background which precludes its use on pre-existing strains.
The molecular mechanism of the HaloTag system is based on a mutant bacterial haloalkane dehalogenase enzyme from Rhodococcus rhodochrous, in which Phe272 is substituted by His272.
