Giannoni P, Scarabelli L, Orunesu M, Cesarone C F
Istituto di Fisiologia Generale, Università di Genova.
Ital J Biochem. 1995 May-Jun;44(3):129-36.
DNA topoisomerase I activity (topo I) is known to be inhibited by poly(ADP-ribosyl)ation. Both poly(ADP-ribose)polymerase (pADPRP) and DNA topoisomerase I participate to major biological events, such as DNA transcription, repair and synthesis. It has been shown that thyroid hormones, such as 3,5,3'-triiodothyronine (T3), stimulate DNA transcription and down-regulate pADPRP activity. Using an in vitro model, we have studied the poly(ADP-ribosyl)ation of topo I, in vitro, in the presence of T3. T3 treatment of pADPRP inhibits the enzyme up to 75-80% of control activity. DNA topoisomerase I relaxing activity was determined on supercoiled plasmid DNA, and topoisomers were separated by agarose gel electrophoresis. Poly(ADP-ribosyl)ation completely inhibits the relaxing activity of topo I, with respect to non-ribosylated controls, but the activity remains unaffected when pADPRP is inactivated by heat or treated with specific inhibitors, such as 3-aminobenzamide (3ABA). In this study we show that treatment of pADPRP with T3 reduces the inhibition on topo I. In this system 10(-8) M T3 was effective in maintaining almost all topo I activity, even though modifications in processivity and distributivity of the reaction were noted. These data support a close relationship between pADPRP and topo I in hormone-stimulated DNA transcription.
已知DNA拓扑异构酶I活性（拓扑异构酶I）会受到聚（ADP - 核糖基）化的抑制。聚（ADP - 核糖）聚合酶（pADPRP）和DNA拓扑异构酶I都参与了诸如DNA转录、修复和合成等重大生物学事件。研究表明，甲状腺激素，如3,5,3'-三碘甲状腺原氨酸（T3），可刺激DNA转录并下调pADPRP活性。我们使用体外模型，研究了在T3存在下体外拓扑异构酶I的聚（ADP - 核糖基）化情况。用T3处理pADPRP可使该酶活性抑制至对照活性的75 - 80%。在超螺旋质粒DNA上测定DNA拓扑异构酶I的解旋活性，通过琼脂糖凝胶电泳分离拓扑异构体。与未进行核糖基化的对照相比，聚（ADP - 核糖基）化完全抑制了拓扑异构酶I的解旋活性，但当pADPRP经加热失活或用特定抑制剂如3 - 氨基苯甲酰胺（3ABA）处理时，该活性不受影响。在本研究中，我们表明用T3处理pADPRP可减少对拓扑异构酶I的抑制。在该系统中，10^(-8) M的T3能够有效维持几乎所有拓扑异构酶I的活性，尽管观察到反应的持续合成能力和分布能力有所改变。这些数据支持了在激素刺激的DNA转录过程中pADPRP与拓扑异构酶I之间存在密切关系。
