CAG promoter

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.

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 (two exons and an intron) 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.

References

  1. ↑ Okabe M, Ikawa M, Kominami K, Nakanishi T, Nishimune Y. 'Green mice' as a source of ubiquitous green cells. FEBS Lett. 1997 May 5;407(3):313-9. PMID 9175875
  2. ↑ Alexopoulou AN, Couchman JR, and Whiteford JR. 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, 2008, PMID 18190688.
  3. ↑ Miyazaki, J; Takaki, S; Araki, K; Tashiro, F; Tominaga, A; Takatsu, K; Yamamura, K (Jul 15, 1989). "Expression vector system based on the chicken beta-actin promoter directs efficient production of interleukin-5.". Gene 79 (2): 269–77. doi:10.1016/0378-1119(89)90209-6. PMID 2551778.
  4. ↑ Niwa, H; Yamamura, K; Miyazaki, J (Dec 15, 1991). "Efficient selection for high-expression transfectants with a novel eukaryotic vector.". Gene 108 (2): 193–9. doi:10.1016/0378-1119(91)90434-d. PMID 1660837.


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