Hurley, L., Brooks, T. A., & Hurley, L. -. (2010). Targeting MYC Expression through G-Quadruplexes. Genes & cancer, 1(6).
In this review, the authors describe a novel mechanism for control of MYC expression that involves a four-stranded DNA structure, termed a G-quadruplex, amenable to small molecule targeting. The DNA element involved in this mechanism, the nuclease hypersensitive element III(1) (NHE III(1)), is just upstream of the P1 promoter and is subjected to dynamic stress (negative superhelicity) resulting from transcription. This is sufficient to convert the duplex DNA to a G-quadruplex on the purine-rich strand and an i-motif of the pyrimidine-rich strand, which displaces the activating transcription factors to silence gene expression. Specific proteins have been identified, NM23-H2 and nucleolin, that resolve and fold the G-quadruplex to activate and silence MYC expression, respectively. Inhibition of the activity of NM23-H2 molecules that bind to the G-quadruplex silences gene expression, and redistribution of nucleolin from the nucleolus to the nucleoplasm is expected to inhibit MYC. The authors also describe the mechanism of action of Quarfloxin, a first-in-class G-quadruplex-interactive compound that involves the redistribution of nucleolin from the nucleolus to the nucleoplasm. G-quadruplexes have been best known as test-tube oddities for more than four decades. However, during the past decade, they have emerged as likely players in a number of important biological processes, including transcriptional control. Only time will tell if these odd DNA structures will assume the role of an established receptor class, but it is clear from the scientific literature that there is a dramatic increase in interest in this little-known area in the past few years.
Hurley, L. H. (1980). Elucidation and formulation of novel biosynthetic pathways leading to the pyrrolo[1,4]benzodiazepine antibiotics anthramycin, tomaymycin, and sibiromycin. Accounts of Chemical Research, 13(8), 263-269.
Hurley, L. H., Needham-VanDevanter, D., & Lee, C. (1987). Demonstration of the asymmetric effect of CC-1065 on local DNA structure using a site-directed adduct in a 117-base-pair fragment from M13mp1. Proceedings of the National Academy of Sciences of the United States of America, 84(18), 6412-6416.
PMID: 2819875;PMCID: PMC299086;Abstract:
Using DNase I and Alu I endonuclease analysis of a site-directed CC-1065-[N3-adenine]DNA adduct in a 117-base-pair fragment from M13mp1 DNA, we have demonstrated that CC-1065 produces an asymmetric effect on DNA conformation that extends more than one helix turn to the 5' side of the covalently modified adenine. CC-1065 is a potent antitumor antibiotic produced by Streptomyces zelensis, which is believed to mediate its cytotoxic effects through covalent binding to DNA. Previous studies have demonstrated that CC-1065 binds covalently to N3 of adenine and lies within the minor groove of DNA spanning a 4-base-pair sequence to the 5' side of the modified adenine. DNase I footprinting of this site-directed CC-1065-DNA adduct on the noncovalently modified strand shows that inhibition of cleavage occurs over a 12-base region, which is bordered on the 3' side by a site of 2-fold enhancement of cleavage. On the covalently modified strand a much less pronounced inhibition/enhancement pattern of cleavage occurs as far as 11 bases to the 5' side of the covalently modified adenine. While Hae III is able to cleave the DNA on both strands on the 3' side of the covalently modified adenine, Alu I is only able to cleave the covalently modified strand on the 5' side of the adduct. By taking into account the recently published structure of DNase I, we are able to interpret these results and develop a model for the effect of CC-1065 on local DNA structure. In this model, we propose selective drug-induced distortion of the covalently modified strand as a consequence of the alkylation of adenine by CC-1065.
Henderson, D., & Hurley, L. H. (1996). Specific targeting of protein-DNA complexes by DNA-reactive drugs (+)- CC-1065 and pluramycins. Journal of Molecular Recognition, 9(2), 75-87.
PMID: 8877797;Abstract:
To gain insight into the interactions between transcriptional factor proteins and DNA, the DNA-reactive drugs (+)-CC-1065 and pluramycin were used to target specific protein-DNA complexes. The structural features of the complex between the transcriptional activator Sp1 and the 21-base-pair repeat of the early promoter region of SV40 DNA were examined using hydroxyl-radical footprinting; (+)-CC-1065, a sequence-specific minor groove bending probe; and circularization experiments. The results show that the 21-base-pair repeat region has an intrinsically in-phase bent structure that is stabilized upon saturation Sp1 binding by protein-DNA and protein-protein interactions to produce a looping structure. The intercalating drug pluramycin was used to probe the structural details of the interaction between the TATA binding protein (TBP) and the TATA box DNA sequence. TBP, which directs initiation of RNA transcription, exhibits two-fold symmetry and apparently interacts with the TATA box in a symmetrical fashion. However, the interaction results in an asymmetric effect, in that transcription is initiated only in the downstream direction. Using pluramycin as a probe, it was determined that TBP binding to the human myoglobin TATA sequences enhances pluramycin reactivity at a site immediately downstream of the TATA box. The implications on transcriptional control of ternary complexes comprised of transcriptional factors, DNA, and DNA-reactive compounds will be presented.
Brahme, N. M., Gonzalez, J. E., Rolls, J. P., Hessler, E. J., Mizsak, S., & Hurley, L. H. (1984). Biosynthesis of the lincomycins. 1. Studies using stable isotopes on the biosynthesis of the propyl- and ethyl-L-hygric acid moieties of lincomycins A and B. Journal of the American Chemical Society, 106(25), 7873-7878.
Abstract:
The biosynthesis of the propyl-L-hygric acid and ethyl-L-hygric acid moieties of lincomycins A and B has been examined by using deuterated and carbon-13 labeled precursors in combination with carbon-13 NMR and mass spectral analysis. The results, using specifically deuterated tyrosine, DOPA, and methionine, demonstrate that tyrosine is converted via DOPA to an intermediate that undergoes aromatic ring cleavage most probably via a 2,3-extradiol cleavage reaction. An experiment using D-(13C6)glucose in combination with analysis of the 13C-13C spin-coupling patterns in lincomycin A and propyl-L-hygric acid permits the determination of those carbon atoms that remain together during the biosynthesis of lincomycin A. Glucose is converted via glycolysis and the hexose monophosphate shunt to phosphoenolpyruvate and erythrose 4-phosphate, respectively, which are in turn converted via the shikimic acid pathway to tyrosine and hence into DOPA. The subsequent reactions after DOPA are consistent with the 2,3-extradiol cleavage pathway and an addition of a C-1 unit from methionine to give rise to the terminal methyl group of the propyl side chain. These results are now consistent with those obtained for the C2- and C3-proline moieties found in anthramycin, tomaymycin, and sibiromycin that are also biosynthetically derived from tyrosine. © 1984 American Chemical Society.
