c-MYC G-quadruplex binding by the RNA polymerase I inhibitor BMH-21 and analogues revealed by a combined NMR and biochemical Approach

• Published in: Biochimica et biophysica acta Vol. 1862; no. 3; pp. 615 - 629
• Main Authors: Musso, Loana, Mazzini, Stefania, Rossini, Anna, Castagnoli, Lorenzo, Scaglioni, Leonardo, Artali, Roberto, Di Nicola, Massimo, Zunino, Franco, Dallavalle, Sabrina
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2018
• Subjects: Antitumor agents; BMH-21; c-MYC; G-quadruplex; Molecular modelling; NMR; BMH-21; NMR; Antitumor agents; Molecular modelling; c-MYC; G-quadruplex
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2017.12.002

Pyridoquinazolinecarboxamides have been reported as RNA polymerase I inhibitors and represent a novel class of potential antitumor agents. BMH-21, was reported to intercalate with GC-rich rDNA, resulting in nucleolar stress as a primary mechanism of cytotoxicity. The interaction of BMH-21 and analogues with DNA G-quadruplex structures was studied by NMR and molecular modelling. The cellular response was investigated in a panel of human tumor cell lines and protein expression was examined by Western Blot analysis. We explored the ability of BMH-21 and its analogue 2 to bind to G-quadruplex present in the c-MYC promoter, by NMR and molecular modelling studies. We provide evidence that both compounds are not typical DNA intercalators but are effective binders of the tested G-quadruplex. The interaction with c-MYC G-quadruplex was reflected in down-regulation of c-Myc expression in human tumor cells. The inhibitory effect was almost complete in lymphoma cells SUDHL4 characterized by overexpression of c-Myc protein. This downregulation reflected an early and persistent modulation of cMyc mRNA. Given the relevance of c-MYC in regulation of ribosome biogenesis, it is conceivable that the inhibition of c-MYC contributes to the perturbation of nuclear functions and RNA polymerase I activity. Similar experiments with CX-5461, another RNA polymerase I transcription inhibitor, indicate the same behaviour in G-quadruplex stabilization. Our results support the hypothesis that BMH-21 and analogue compounds share the same mechanism, i.e. G-quadruplex binding as a primary event of a cascade leading to inhibition of RNA polymerase I and apoptosis. [Display omitted] •A NMR study of interaction of BMH-21 with quadruplex DNA oligomers was undertaken.•BMH-21, its analogue 2 and CX-5461 bind to Gquadruplex present in the c-MYC promoter.•The compounds down-regulate c-MYC expression in human tumor cells.