Conditional protein splicing: a new tool to control protein structure and function in vitro and in vivo.
Protein splicing is a naturally occurring process in which an intervening intein domain excises itself out of a precursor polypeptide in an autocatalytic fashion with concomitant linkage of the two flanking extein sequences by a native peptide bond. We have recently reported an engineered split VMA intein whose splicing activity in trans between two polypeptides can be triggered by the small molecule rapamycin. In this report, we show that this conditional protein splicing (CPS) system can be used in mammalian cells. Two model constructs harboring maltose-binding protein (MBP) and a His-tag as exteins were expressed from a constitutive promoter after transient transfection. The splicing product MBP-His was detected by Western blotting and immunoprecipitation in cells treated with rapamycin or a nontoxic analogue thereof. No background splicing in the absence of the small-molecule inducer was observed over a 24-h time course. Product formation could be detected within 10 min of addition of rapamycin, indicating the advantage of the posttranslational nature of CPS for quick responses. The level of protein splicing was dose dependent and could be competitively attenuated with the small molecule ascomycin. In related studies, the geometric flexibility of the CPS components was investigated with a series of purified proteins. The FKBP and FRB domains, which are dimerized by rapamycin and thereby induce the reconstitution of the split intein, were fused to the extein sequences of the split intein halves. CPS was still triggered by rapamycin when FKBP and FRB occupied one or both of the extein positions. This finding suggests yet further applications of CPS in the area of proteomics. In summary, CPS holds great promise to become a powerful new tool to control protein structure and function in vitro and in living cells.
Mootz
Henning D
HD
Laboratory of Synthetic Protein Chemistry, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Blum
Elyse S
ES
Tyszkiewicz
Amy B
AB
Muir
Tom W
TW
D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics*; D019281:Dimerization; D006367:HeLa Cells; D006639:Histidine / Q000235:genetics; D006801:Humans; D020104:Immunophilins / Q000737:chemistry / Q000235:genetics*; D058619:Maltose-Binding Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor); D011401:Promoter Regions, Genetic; D019154:Protein Splicing; D017434:Protein Structure, Tertiary; D020123:Sirolimus / Q000031:analogs & derivatives / Q000494:pharmacology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013329:Structure-Activity Relationship; D058570:TOR Serine-Threonine Kinases; D016559:Tacrolimus / Q000031:analogs & derivatives* / Q000494:pharmacology; D022021:Tacrolimus Binding Proteins / Q000737:chemistry / Q000235:genetics*; D014162:Transfection; D015032:Zinc / Q000737:chemistry / Q000494:pharmacology
D002352:Carrier Proteins; D058619:Maltose-Binding Proteins; D006639:Histidine; C058028:immunomycin; D017853:Phosphotransferases (Alcohol Group Acceptor); C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D022021:Tacrolimus Binding Proteins; D020104:Immunophilins; D015032:Zinc; D020123:Sirolimus; D016559:Tacrolimus