Mutagenesis by reversible promoter insertion to study the activation of NF-kappaB.
Genetic dissection of signaling pathways in mammalian cells involves screening or selecting phenotypic mutants obtained by a variety of techniques. Limitations in current methods include inadequate genome coverage and difficulty in validating the link between mutation and phenotype. We describe an improved method for insertional mutagenesis with retroviral vectors and show that the ability to induce mutations increases greatly if a randomly inserted promoter directs transcription into the host DNA. The mutant phenotype is due to the expression of a hybrid transcript derived from the vector and the insertion site. Because other alleles of the affected gene remain intact, the phenotype is dominant, but is reversible by inactivating the promoter, for example, by site-specific recombination. Importantly, in mutant clones with multiple inserts, limited excision yields progeny with different patterns of inserts remaining. Characterizing these progeny allows the mutant phenotype to be associated with a specific target gene. Relative simplicity and robust target validation make the method suitable for a broad range of applications. We have used this technique to search for proteins that regulate NF-kappaB-dependent signaling in human cells. Two validated targets are the relA gene, which codes for the NF-kappaB p65 subunit, and the NF-kappaB regulator act1. Overexpression of the corresponding proteins, caused by insertion of a promoter into the first intron of each gene, leads to NF-kappaB-dependent secretion of factors that activate NF-kappaB through cell-surface receptors, establishing an autocrine loop.
Kandel
Eugene S
ES
Department of Molecular Biology, Lerner Research Institute, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
Lu
Tao
T
Wan
Youzhong
Y
Agarwal
Mukesh K
MK
Jackson
Mark W
MW
Stark
George R
GR
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D015152:Blotting, Northern; D015139:Blotting, Southern; D015153:Blotting, Western; D002460:Cell Line; D017931:DNA Primers; D005786:Gene Expression Regulation; D005822:Genetic Vectors / Q000235:genetics; D049452:Green Fluorescent Proteins; D006801:Humans; D016254:Mutagenesis, Insertional / Q000379:methods*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D011401:Promoter Regions, Genetic / Q000235:genetics; D012190:Retroviridae; D015398:Signal Transduction / Q000235:genetics*; D051996:Transcription Factor RelA; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins
D048868:Adaptor Proteins, Signal Transducing; D017931:DNA Primers; D016328:NF-kappa B; C414202:TRAF3IP2 protein, human; D051996:Transcription Factor RelA; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins; D049452:Green Fluorescent Proteins