Thomas T J, Thomas T
Department of Medicine, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick 08903.
J Biomol Struct Dyn. 1990 Jun;7(6):1221-35. doi: 10.1080/07391102.1990.10508561.
We studied the effects of hexammine and tris(ethylene diamine) complexes of rhodium on the conformation of poly(dG-dC).poly(dG-dC) and poly(dG-m5dC).poly(dG-m5dC) using spectroscopic techniques and an enzyme immunoassay. Circular dichroism spectroscopic measurements showed that Rh(NH3)6(3+) provoked a B-DNA----Z-DNA----psi-DNA conformational transition in poly(dG-dC).poly(dG-dC). Using the enzyme immunoassay technique with a monoclonal anti-Z-DNA antibody, we found that the left-handedness of the polynucleotide was maintained in the psi-DNA form. In addition, we compared the efficacy of Rh(NH3)6(3+) and Rh(en)3(3+) to provoke the Z-DNA conformation in poly(dG-dC).poly(dG-dC) and poly(dG-m5dC.poly(dG-m5dC). The concentrations of Rh(NH3)6(3+) and Rh(en)3(3+) at the midpoint B-DNA----Z-DNA transition of poly(dG-dC).poly(dG-dC) were 48 +/- 2 and 238 +/- 2 microM, respectively. The psi-DNA form of poly(dG-dC).poly(dG-dC) was stabilized at 500 microM Rh(NH3)6(3+). With poly(dG-m5dC).poly(dg-m5dC), both counterions provoked the Z-DNA form at approximately 5 microM and stabilized the polynucleotide in this form up to 1000 microM concentration. These results show that trivalent complexes of Rh have a profound influence on the conformation of poly(dG-dC).poly(dG-dC) and its methylated derivative. Furthermore, the Rh complexes are capable of maintaining the Z-DNA form at concentration ranges far higher than that of other trivalent complexes. Our results also demonstrate that the efficacy of trivalent inorganic complexes to induce the B-DNA to Z-DNA transition of poly(dG-dC).poly(dG-dC) and poly(dG-m5dC).poly(dG-m5dC) is dependent on the nature of the ligand as well as the polynucleotide modification. Differences in charge density and hydration levels of counterions or base sequence- and counterion-dependent specific interactions between DNA and metal complexes might be possible mechanisms for the observed effects.
我们运用光谱技术和酶免疫测定法，研究了铑的六氨络合物和三（乙二胺）络合物对聚（dG-dC）·聚（dG-dC）以及聚（dG-m5dC）·聚（dG-m5dC）构象的影响。圆二色光谱测量表明，Rh(NH3)6(3+)可促使聚（dG-dC）·聚（dG-dC）发生从B-DNA到Z-DNA再到ψ-DNA的构象转变。使用单克隆抗Z-DNA抗体的酶免疫测定技术，我们发现多核苷酸的左旋性在ψ-DNA形式中得以保持。此外，我们比较了Rh(NH3)6(3+)和Rh(en)3(3+)在聚（dG-dC）·聚（dG-dC）以及聚（dG-m5dC）·聚（dG-m5dC）中促使形成Z-DNA构象的效果。在聚（dG-dC）·聚（dG-dC）的中点B-DNA到Z-DNA转变时，Rh(NH3)6(3+)和Rh(en)3(3+)的浓度分别为48±2μM和238±2μM。聚（dG-dC）·聚（dG-dC）的ψ-DNA形式在500μM的Rh(NH3)6(3+)时得以稳定。对于聚（dG-m5dC）·聚（dg-m5dC），两种抗衡离子在约5μM时促使形成Z-DNA形式，并在高达1000μM的浓度下使多核苷酸保持这种形式。这些结果表明，铑的三价络合物对聚（dG-dC）·聚（dG-dC）及其甲基化衍生物的构象有深远影响。此外，铑络合物能够在远高于其他三价络合物的浓度范围内保持Z-DNA形式。我们的结果还表明，三价无机络合物诱导聚（dG-dC）·聚（dG-dC）和聚（dG-m5dC）·聚（dG-m5dC）从B-DNA到Z-DNA转变的效果取决于配体的性质以及多核苷酸的修饰。抗衡离子的电荷密度和水合水平差异，或者DNA与金属络合物之间碱基序列和抗衡离子依赖性的特异性相互作用，可能是观察到这些效应的潜在机制。
