Chasovskikh Sergey, Dimtchev Alexandre, Smulson Mark, Dritschilo Anatoly
Department of Radiation Medicine, Georgetown University Medical Center, Washington, DC 20057, USA.
Cytometry A. 2005 Nov;68(1):21-7. doi: 10.1002/cyto.a.20187.
Poly(ADP-ribose)polymerase-1 (PARP-1) binds to single and double-stranded breaks in DNA, but less well known is its affinity for undamaged DNA. Previously, we have shown that PARP-1 also binds to the hairpin structures in DNA models. The mechanism underlying these interactions remains to be defined.
We analyzed atomic force microscopy (AFM) images of complex of PARP-1 proteins with supercoiled plasmids containing cruciform structures. Using volume measurement analysis of molecules of PARP-1, we determined the numbers of PARP-1 molecules interacting with supercoiled DNA plasmids containing one cruciform structure. We also determined the extent of supercoiling of plasmids.
Our observations show that PARP-1 binds to sequences that transition from B-DNA to cruciform structures. PARP-1 is present at the ends of hairpin arms, sites containing a 4-base single-stranded DNA. Furthermore, interaction of PARP-1 with supercoiled plasmids leads to a more relaxed plasmid-DNA conformation.
Binding of PARP-1 to cruciform DNA offers insight into possible mechanisms underlying with changes in DNA conformation. These observations may offer insight into mechanisms involving DNA conformation related to process such as DNA repair and transcription.
聚（ADP - 核糖）聚合酶 - 1（PARP - 1）可与DNA中的单链和双链断裂结合，但其与未受损DNA的亲和力却鲜为人知。此前，我们已经表明PARP - 1也能与DNA模型中的发夹结构结合。这些相互作用的潜在机制仍有待确定。
我们分析了PARP - 1蛋白与含有十字形结构的超螺旋质粒复合物的原子力显微镜（AFM）图像。通过对PARP - 1分子进行体积测量分析，我们确定了与含有一个十字形结构的超螺旋DNA质粒相互作用的PARP - 1分子数量。我们还测定了质粒的超螺旋程度。
我们的观察结果表明，PARP - 1与从B - DNA转变为十字形结构的序列结合。PARP - 1存在于发夹臂的末端，即含有4个碱基单链DNA的位点。此外，PARP - 1与超螺旋质粒的相互作用导致质粒 - DNA构象更加松弛。
PARP - 1与十字形DNA的结合为DNA构象变化的潜在机制提供了见解。这些观察结果可能有助于深入了解涉及DNA构象的机制，如DNA修复和转录等过程。
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