Turning off Transcription of the bcl-2 Gene by Stabilizing the bcl-2 Promoter Quadruplex with Quindoline Derivatives

Abstract

Human bcl-2 gene is an apoptosis-related oncogene containing a GC-rich sequence which is located upstream from P1 promoter and has the potential to form G-quadruplex structures. However, the regulatory role of the quadruplex and the effect of its ligands on bcl-2 have not been clarified. Here, we demonstrated that the G-quadruplex structure was disrupted when partial mutation of G --> A was made, resulting in a 2-fold increase in basal transcriptional activity of bcl-2 promoter. Quindoline derivatives, the highly active G-quadruplex ligands developed by our group, could significantly suppress bcl-2 transcriptional activation but had less effect on mutated bcl-2 transcription. These results provided direct evidence that G-quadruplex structure formed in bcl-2 promoter region could function as a transcriptional repressor element, and G-quadruplex specific ligands could regulate the transcription of bcl-2 through stabilization of quadruplex structure. The results further indicated that quindoline derivatives could induce apoptosis of HL-60 tumor cells.

Assessment of gene promoter G-quadruplex binding and modulation by a naphthalene diimide derivative in tumor cells

“…2D). These data are in keeping with those reported in literature and concerning the biophysical characterization of G-4 conformers of the selected genes in the presence or absence of specific ligands (11,(29)(30)(31). The evidence that H-NDI-NMe 2 maintained a parallel MYC G-4 conformer deals with the observed increase in the gene expression levels in H69 cells upon NDI exposure, as also suggested by the findings that polyamines and CNBP both stimulate MYC transcriptional activity by favouring the formation of a parallel G-4 structure within the gene promoter (26,28).…”

“…Conversely, different layers of complexity have been reported regarding the G-4-forming sequences within the BCL2 promoter (36,37). In fact, it has been demonstrated that BCL2 may form diverse G-4 structures with a parallel-or mixed-type conformation, the biological significance of which still need to be disclosed (31). However, the existence of G-4-forming sequences within the BCL2 promoter points towards their possible role in modulating gene expression.…”

The G-quadruplex ligand, SYUIQ-FM05, targets proto-oncogene c-kittranscription and induces apoptosis in K562 cells

“…Our data demonstrated that the down-regulation of Bcl-2 expression corresponded to the decrease in p-MEK and p-ERK, which increased Bax expression. SYUIQ-FM05 suppresses bcl-2 transcriptional activation through a stabilization of a GC-rich sequence in its promoter (Todd et al, 2007;Wang et al, 2010). In our study, 10.0 and 20.0 nM SYUIQ-FM05 also inhibited bcl-2 transcription, but only a slight difference in the expression of Bcl-2 protein was detected.…”

“…SYUIQ-FM05 is a 5-N-methyl quindoline derivative that exerts remarkable effects on cell growth arrest and cellular senescence and inhibits telomere elongation in leukemia cells (Lu et al, 2008). SYUIQ-FM05 inhibits the transcription of the bcl-2 gene by stabilizing the promoter quadruplex in HL60 cells (Wang et al, 2010). This inhibition suggests that these quindoline derivatives exert similar effects on quadruplex structure in other genes.…”

Determination of SYUIQ-F5, a Novel Telomerase Inhibitor and Anti-tumor Lead-Compound, in Tissues and Plasma Samples by LC–MS–MS: Application to a Tissue Distribution Study in Rat

“…1) is a novel quindoline derivative synthesized by the School of Pharmaceutical Sciences, Sun Yat-sen University. SYUIQ-F5 has been shown to interfere with telomere replication by blocking the elongation step catalyzed by both telomerasedependent and telomerase-independent mechanisms like its homologues such SYUIQ-5 and SYUIQ-FM05, which were also synthesized by Sun Yat-sen University [1][2][3][4][5]. Considerable evidence suggested that stabilization of G-quadruplex structures could directly inhibit telomerase activity and might cause down-regulation for the transcription of some oncogenes including G-quadruplex forming sequence in their promoters, such as bcl-2, c-myc, and c-kit [1,[6][7][8].…”