tailieunhanh - Báo cáo khoa học: Aggregative organization enhances the DNA end-joining process that is mediated by DNA-dependent protein kinase

The occurrence of DNA double-strand breaks in the nucleus provokes in its structural organization a large-scale alteration whose molecular basis is still mostly unclear. Here, we show that double-strand breaks trigger pref-erential assembly of nucleoproteins in human cellular fractions and that they mediate the separation of large protein–DNA aggregates from aque-ous solution. | ềFEBS Journal Aggregative organization enhances the DNA end-joining process that is mediated by DNA-dependent protein kinase Masahiko Takahagi and Kouichi Tatsumi Research Center for Radiation Safety National institute of RadiologicalSciences Chiba Japan Keywords coacervate DNA aggregation DNA endjoining DNA-PK S MAR Correspondence K. Tatsumi Research Center for Radiation Safety National institute of Radiological Sciences 9-1 Anagawa 4 Inage-ku Chiba 263-8555 Japan Fax 81 43 255 6497 Tel 81 43 206 3087 E-mail tatsumi@ Received 7 April2006 accepted 11 May 2006 doi The occurrence of DNA double-strand breaks in the nucleus provokes in its structural organization a large-scale alteration whose molecular basis is still mostly unclear. Here we show that double-strand breaks trigger preferential assembly of nucleoproteins in human cellular fractions and that they mediate the separation of large protein-DNA aggregates from aqueous solution. The interaction among the aggregative nucleoproteins presents a dynamic condition that allows the effective interaction of nucleoproteins with external molecules like free ATP and facilitates intrinsic DNA end-joining activity. This aggregative organization is functionally coacervate-like. The key component is DNA-dependent protein kinase DNA-PK which can be characterized as a DNA-specific aggregation factor as well as a nuclear scaffold matrix-interactive factor. In the context of aggregation the kinase activity of DNA-PK is essential for efficient DNA end-joining. The massive and functional concentration of nucleoproteins on DNA in vitro may represent a possible status of nuclear dynamics in vivo which probably includes the DNA-PK-dependent response to multiple double-strand breaks. DNA double-strand breaks DSBs are a serious threat to the genetic integrity of organisms causing cell death if not repaired. The repair mechanism for DSBs resides not only in catalytic processes but also in the .