Editing Dihydrofolate reductase (section)

== As a research tool ==

DHFR has been used as a tool to detect [[protein–protein interactions]] in a [[protein-fragment complementation assay]] (PCA), using a split-protein approach.<ref name="Tarrasov2008">{{cite journal | vauthors = Tarassov K, Messier V, Landry CR, Radinovic S, Serna Molina MM, Shames I, Malitskaya Y, Vogel J, Bussey H, Michnick SW | title = An in vivo map of the yeast protein interactome | journal = Science | volume = 320 | issue = 5882 | pages = 1465–70 | date = June 2008 | pmid = 18467557 | doi = 10.1126/science.1153878 | bibcode = 2008Sci...320.1465T | s2cid = 1732896 | url = http://www-nmr.cabm.rutgers.edu/academics/biochem694/reading/Tarassov_et_al_2008.pdf }}</ref>

DHFR-lacking [[Chinese hamster ovary cell|CHO cells]] are the most commonly used [[cell line]] for the production of recombinant proteins. These cells are [[transfection|transfected]] with a [[plasmid]] carrying the ''dhfr'' gene and the gene for the recombinant protein in a single [[expression system]], and then subjected to [[selection (biology)|selective conditions]] in thymidine-lacking [[growth medium|medium]]. Only the cells with the exogenous DHFR gene along with the gene of interest survive. Supplementation of this medium with methotrexate, a competitive inhibitor of DHFR, can further select for those cells expressing the highest levels of DHFR, and thus, select for the top recombinant protein producers.<ref>{{cite book | vauthors = Ng SK |chapter=Generation of High-Expressing Cells by Methotrexate Amplification of Destabilized Dihydrofolate Reductase Selection Marker |title=Protein Expression in Mammalian Cells |series=Methods in Molecular Biology |date=2012 |volume=801 |pages=161–172 |doi=10.1007/978-1-61779-352-3_11 |pmid=21987253|isbn=978-1-61779-351-6 }}</ref>