Targeting the G-quadruplex-forming region near the P1 promoter in the human BCL-2 gene with the cationic porphyrin TMPyP4 and with the complementary C-rich strand.
The B-cell lymphoma-2 (bcl-2) gene contains a region that has been implicated in the regulation of bcl-2 gene expression. This region can form G-quadruplex structures in solution [J.X. Dai, T.S. Dexheimer, D. Chen, M. Carver, A. Ambrus, R.A. Jones, D.Z. Yang, An intramolecular G-quadruplex structure with mixed parallel/antiparallel G-strands formed in the human BCL-2 promoter region in solution, J. Am. Chem. Soc. 128 (2006) 1096-1098.]. Here, we examined the acid-base and conformational equilibria of this G-quadruplex-forming region (BCL2G), as well as its interaction with both the porphyrin TMPyP4 and with the complementary C-rich strand. We used molecular absorption and circular dichroism techniques, in tandem with multivariate analysis tools. The results revealed the formation of an interaction complex BCL2G:TMPyP4 with a stoichiometry of 1:2 and an equilibrium constant equal to 5.0 (+/-2.3) x 10(13) M(-2). Addition of the complementary C-rich strand to BCL2G induces the predominant formation of the Watson-Crick double-helix with an equilibrium constant equal to 10(7.7) M(-1) (at pH 7.1). Finally, the pH-induced formation of quadruplex structures from the Watson-Crick double-helix is characterized.
Del Toro
Miquel
M
Department of Analytical Chemistry, University of Barcelona, Marti i Franques 1-11, E-08028 Barcelona, Spain.
Bucek
Pavel
P
Aviñó
Anna
A
Jaumot
Joaquim
J
González
Carlos
C
Eritja
Ramon
R
Gargallo
Raimundo
R
D002942:Circular Dichroism; D054856:G-Quadruplexes; D019254:Genes, bcl-2; D006801:Humans; D015999:Multivariate Analysis; D009841:Oligonucleotides / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry; D011401:Promoter Regions, Genetic
D009841:Oligonucleotides; D011166:Porphyrins; C021096:tetra(4-N-methylpyridyl)porphine