title: Binding to the minor groove of the double-strand, tau protein prevents DNA from damage by peroxidation.
abstract: Tau, an important microtubule associated protein, has been found to bind to DNA, and to be localized in the nuclei of both neurons and some non-neuronal cells. Here, using electrophoretic mobility shifting assay (EMSA) in the presence of DNA with different chain-lengths, we observed that tau protein favored binding to a 13 bp or a longer polynucleotide. The results from atomic force microscopy also showed that tau protein preferred a 13 bp polynucleotide to a 12 bp or shorter polynucleotide. In a competitive assay, a minor groove binder distamycin A was able to replace the bound tau from the DNA double helix, indicating that tau protein binds to the minor groove. Tau protein was able to protect the double-strand from digestion in the presence of DNase I that was bound to the minor groove. On the other hand, a major groove binder methyl green as a negative competitor exhibited little effect on the retardation of tau-DNA complex in EMSA. This further indicates the DNA minor groove as the binding site for tau protein. EMSA with truncated tau proteins showed that both the proline-rich domain (PRD) and the microtubule-binding domain (MTBD) contributed to the interaction with DNA; that is to say, both PRD and MTBD bound to the minor groove of DNA and bent the double-strand, as observed by electron microscopy. To investigate whether tau protein is able to prevent DNA from the impairment by hydroxyl free radical, the chemiluminescence emitted by the phen-Cu/H(2)O(2)/ascorbate was measured. The emission intensity of the luminescence was markedly decreased when tau protein was present, suggesting a significant protection of DNA from the damage in the presence of hydroxyl free radical.
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wei
authors.forename: Mei-Hua
authors.initials: MH
authors.lastname: Qu
authors.forename: Xing-Sheng
authors.initials: XS
authors.lastname: Wang
authors.forename: Lan
authors.initials: L
authors.lastname: Chen
authors.forename: Dong-Liang
authors.initials: DL
authors.lastname: Wang
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.forename: Qian
authors.initials: Q
authors.lastname: Hua
authors.forename: Rong-Qiao
authors.initials: RQ
authors.lastname: He
mesh_terms: D001665:Binding Sites; D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D004249:DNA Damage; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D017665:Hydroxyl Radical / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D011392:Proline / Q000737:chemistry / Q000378:metabolism; D016875:tau Proteins / Q000138:chemical synthesis / Q000378:metabolism*
chemical_list: D016875:tau Proteins; D017665:Hydroxyl Radical; D004247:DNA; D011392:Proline