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

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

  • Biochim Biophys Acta Gen Subj. 2018 Mar;1862(3):615-629. doi: 10.1016/j.bbagen.2017.12.002.
Loana Musso 1 Stefania Mazzini 2 Anna Rossini 3 Lorenzo Castagnoli 4 Leonardo Scaglioni 1 Roberto Artali 5 Massimo Di Nicola 3 Franco Zunino 3 Sabrina Dallavalle 1
Affiliations

Affiliations

  • 1 Department of Food, Environmental and Nutritional Sciences, Division of Chemistry and Molecular Biology, Università degli Studi di Milano, via Celoria 2, I-20133 Milano, Italy.
  • 2 Department of Food, Environmental and Nutritional Sciences, Division of Chemistry and Molecular Biology, Università degli Studi di Milano, via Celoria 2, I-20133 Milano, Italy. Electronic address: stefania.mazzini@unimi.it.
  • 3 Fondazione IRCCS, Istituto Nazionale dei Tumori, via Venezian 1, 20133 Milano, Italy.
  • 4 Molecular Targeting Unit, Department of Applied Research and Technological Development, Fondazione IRCCS Istituto Nazionale Tumori, via Venezian 1, 20133 Milano, Italy.
  • 5 Scientia Advice, di Roberto Artali, 20832 Desio, MB, Italy.
Abstract

Background: 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.

Methods: 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.

Results and conclusions: 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.

General significance: 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.

Keywords

Antitumor agents; BMH-21; G-quadruplex; Molecular modelling; NMR; c-MYC.

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