González, V., & Hurley, L. H. (2010). The C-terminus of nucleolin promotes the formation of the c-MYC G-quadruplex and inhibits c-MYC promoter activity. Biochemistry, 49(45), 9706-9714.
PMID: 20932061;PMCID: PMC2976822;Abstract:
Nucleolin, the most abundant nucleolar phosphoprotein of eukaryotic cells, is known primarily for its role in ribosome biogenesis and cell proliferation. It is, however, a multifunctional protein that, depending on the cellular context, can drive either cell proliferation or apoptosis. Our laboratory recently demonstrated that nucleolin can function as a repressor of c-MYC transcription by binding to and stabilizing the formation of a G-quadruplex structure in a region of the c-MYC promoter responsible for controlling 85-90% of c-MYC's transcriptional activity. In this study, we investigate the structural elements of nucleolin that are required for c-MYC repression. The effect of nucleolin deletion mutants on the formation and stability of the c-MYC G-quadruplex, as well as c-MYC transcriptional activity, was assessed by circular dichroism spectropolarimetry, thermal stability, and in vitro transcription. Here we report that nucleolin's RNA binding domains 3 and 4, as well as the arginine-glycine-glycine (RGG) domain, are required to repress c-MYC transcription. © 2010 American Chemical Society.
Ostrander, J. M., Hurley, L. H., McInnes, A. G., Smith, D. G., Walter, J. A., & Wright, J. L. (1980). Proof for the biosynthetic conversion of L-[indole- 15N]tryptophan to [10- 15N]anthramycin using ( 13C, 15N) labelling in conjunction with 13C-NMR and mass spectral analysis. Journal of Antibiotics, 33(10), 1167-1171.
Salazar, M., Thompson, B. D., Kerwin, S. M., & Hurley, L. H. (1996). Thermally induced DNA·RNA hybrid to G-quadruplex transitions: Possible implications for telomere synthesis by telomerase. Biochemistry, 35(50), 16110-16115.
PMID: 8973182;Abstract:
Telomerase is a specialized reverse transcriptase that contains its own RNA template for synthesis of telomeric DNA [Greider, C. W., and Blackburn, E. H. (1989) Nature 337, 331-337; Shippen-Lentz, D., and Blackburn, E. H. (1990) Science 247, 546-552]. The activity of this ribonucleoprotein enzyme has been associated with cancer cells [Kim et al. (1994) Science 266, 2011- 2015] and is thus a potential target for anticancer chemotherapy. Telomeric DNA·RNA hybrids are important intermediates in telomerase function and form after extension of the growing telomere on the telomerase RNA template. Translocation is a critical step in telomerase function and consists of unwinding of the telomeric DNA·telomerase RNA hybrid followed by repositioning of the 3'-end of the extended telomere. A central question in telomerase function is how translocation of the extended telomere occurs in the absence of ATP or GTP. It has been hypothesized that unwinding of the telomeric hybrid may be facilitated by the formation of stable hairpins or G-quadruplexes by the telomere product (i.e., a hybrid to G-quadruplex transition) and that this may provide at least part of the driving force for translocation [Shippen-Lentz and Blackburn. 1990; Zahler et al. (1991) Nature 350, 718-720]. However, so far there has been no effort aimed at examining the possibility that a hybrid/G-quadruplex equilibrium can occur and to what extent this equilibrium depends on buffer and concentration conditions. Examination of these transitions may provide insight into telomerase function and may also provide clues for the development of anti- telomerase agents. Using a model system consisting of the DNA·RNA hybrid d(GGTTAAGGGTTAG)·r(cuaacccuaacc), we present evidence that a thermally induced transition of telomeric DNA·RNA hybrid to G-quadruplex can occur under certain conditions. These results provide support for the hypothesis that G-quadruplex formation by the telomere product may in fact regulate telomerase function at the translocation step (Zahler et al., 1991) and suggest an Achilles' heel for indirectly targeting telomerase. Thus, on the basis of the insight gained from the present studies and the result of Zahler et al. (1991), we propose that ligands that selectively bind or cleave G-quadruplex structures may modulate telomerase processivity.
Hurley, L. H., Rokem, J., & Petrusek, R. L. (1980). Proposed structures of the pyrrolo(1,4)benzodiazepine antibiotic-deoxyribonucleic acid adducts. Biochemical Pharmacology, 29(9), 1307-1310.
Otsuka, H., Mascaretti, O. A., Hurley, L. H., & Floss, H. G. (1980). Stereochemical aspects of the biosynthesis of spectinomycin. Journal of the American Chemical Society, 102(22), 6817-6820.
Abstract:
The biosynthesis of spectinomycin (1) has been studied with specifically and stereospecifically labeled glucose as precursors. The results further define the mode of conversion of glucose into the actinamine (2) moiety of 1 and show that the formation of the cyclitol portion by myo-inositol-1-phosphate synthase involves stereospecific loss of the pro-R hydrogen from C-6 of glucose 6-phosphate. The TDP-glucose oxidoreductase reaction is implicated in the formation of the 4,6-dideoxyhexose moiety of 1 by the demonstration of an intramolecular hydrogen transfer from C-4 to C-6 of the hexose, which occurs with the same stereochemistry, i.e., replacement of OH at C-6 by H-4 in an inversion mode, that has been demonstrated for the enzyme from E. coli and from another streptomycete. © 1980 American Chemical Society.
