The CAG promoter is a strong synthetic promoter frequently used to drive high levels of gene expression in mammalian expression vectors.[1][2]
CAG promoter was constructed in the lab of Dr Jun-ichi Miyazaki[3][4] from the following sequences:
- (C) the cytomegalovirus (CMV) early enhancer element,
- (A) the promoter, the first exon and the first intron of chicken beta-actin gene,
- (G) the splice acceptor of the rabbit beta-globin gene
The resulting synthetic element was used in the pCAGGS expression vector. The initiation codon located at the proximal region of the second exon was disrupted by digesting with NcoI restriction enzyme and replacing the site with a HindIII linker.[3]
Although the whole construct is commonly referred to as the "CAG promoter", it is not a promoter in a strict sense, as it includes a part of the transcribed sequence (the first exon and the first intron of chicken beta-actin gene) and enhancer elements. In addition to the CMV immediate early enhancer, the intron of the chicken beta actin gene contains an enhancer element, which is highly conserved among vertebrates. The 3' part of the promoter has high GC content and is thus refractory to PCR amplification.
Some of the CAG promoter's functions as an effective tool that increases and maintains the expression level of recombinant proteins, as well as increases the expression of transgenes under low temperature conditions.
References
edit- ^ Okabe M, Ikawa M, Kominami K, Nakanishi T, Nishimune Y (May 1997). "'Green mice' as a source of ubiquitous green cells". FEBS Letters. 407 (3): 313–319. Bibcode:1997FEBSL.407..313O. doi:10.1016/s0014-5793(97)00313-x. PMID 9175875. S2CID 22865767.
- ^ Alexopoulou AN, Couchman JR, Whiteford JR (January 2008). "The CMV early enhancer/chicken beta actin (CAG) promoter can be used to drive transgene expression during the differentiation of murine embryonic stem cells into vascular progenitors". BMC Cell Biology. 9: 2. doi:10.1186/1471-2121-9-2. PMC 2254385. PMID 18190688.
- ^ a b Miyazaki J, Takaki S, Araki K, Tashiro F, Tominaga A, Takatsu K, Yamamura K (July 1989). "Expression vector system based on the chicken beta-actin promoter directs efficient production of interleukin-5". Gene. 79 (2): 269–277. doi:10.1016/0378-1119(89)90209-6. PMID 2551778.
- ^ Niwa H, Yamamura K, Miyazaki J (December 1991). "Efficient selection for high-expression transfectants with a novel eukaryotic vector". Gene. 108 (2): 193–199. doi:10.1016/0378-1119(91)90434-d. PMID 1660837.
Further reading
edit- Dou Y, Lin Y, Wang TY, Wang XY, Jia YL, Zhao CP (January 2021). "The CAG promoter maintains high-level transgene expression in HEK293 cells". FEBS Open Bio. 11 (1): 95–104. doi:10.1002/2211-5463.13029. PMC 7780116. PMID 33155423.
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