本期〈Science〉兩篇論文揭示基因調(diào)控點(diǎn)是動(dòng)態(tài)的,，而不是像過(guò)去認(rèn)為的那樣是靜態(tài)的。在真核細(xì)胞中,，DNA是包裝在染色質(zhì)中的,，染色質(zhì)是由調(diào)控基因的組蛋白組成的信息存貯。Yoshiko Mito和同事研究了果蠅染色質(zhì)中組蛋白H3的置換率,，Michael F. Dion和同事在酵母中作了同樣的觀察,。兩個(gè)小組分別報(bào)告了組蛋白H3置換率隨調(diào)控點(diǎn)的不同而有高度的不同，在基因組的編碼區(qū)最“安靜”,，而在已知的染色質(zhì)邊界元件的蛋白質(zhì)結(jié)合點(diǎn)上表現(xiàn)出極高的置換水平,。在這些區(qū)域，表觀遺傳標(biāo)記必須處于不斷變化的狀態(tài),，才能使它們快速和動(dòng)態(tài)的調(diào)制成為可能,。
部分英文原文：
Science 9 March 2007:
Vol. 315. no. 5817, pp. 1408 - 1411
DOI: 10.1126/science.1134004
Histone Replacement Marks the Boundaries of cis-Regulatory Domains
Yoshiko Mito,1,2 Jorja G. Henikoff,1 Steven Henikoff1,3*
Cellular memory is maintained at homeotic genes by cis-regulatory elements whose mechanism of action is unknown. We have examined chromatin at Drosophila homeotic gene clusters by measuring, at high resolution, levels of histone replacement and nucleosome occupancy. Homeotic gene clusters display conspicuous peaks of histone replacement at boundaries of cis-regulatory domains superimposed over broad regions of low replacement. Peaks of histone replacement closely correspond to nuclease-hypersensitive sites, binding sites for Polycomb and trithorax group proteins, and sites of nucleosome depletion. Our results suggest the existence of a continuous process that disrupts nucleosomes and maintains accessibility of cis-regulatory elements.
1 Basic Sciences Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA 98109, USA.
2 Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195, USA.
3 Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
* To whom correspondence should be addressed. E-mail: [email protected]
Science 9 March 2007:
Vol. 315. no. 5817, pp. 1405 - 1408
DOI: 10.1126/science.1134053
Dynamics of Replication-Independent Histone Turnover in Budding Yeast
Michael F. Dion,1* Tommy Kaplan,2,3* Minkyu Kim,4 Stephen Buratowski,4 Nir Friedman,2 Oliver J. Rando1
Chromatin plays roles in processes governed by different time scales. To assay the dynamic behavior of chromatin in living cells, we used genomic tiling arrays to measure histone H3 turnover in G1-arrested Saccharomyces cerevisiae at single-nucleosome resolution over 4% of the genome, and at lower (265 base pair) resolution over the entire genome. We find that nucleosomes at promoters are replaced more rapidly than at coding regions and that replacement rates over coding regions correlate with polymerase density. In addition, rapid histone turnover is found at known chromatin boundary elements. These results suggest that rapid histone turnover serves to functionally separate chromatin domains and prevent spread of histone states.
1 Faculty of Arts and Sciences, Center for Systems Biology, Harvard University, Cambridge, MA 02138, USA.
2 School of Computer Science and Engineering, The Hebrew University, Jerusalem 91904, Israel.
3 Department of Molecular Genetics and Biotechnology, Faculty of Medicine, The Hebrew University, Jerusalem 91120, Israel.
4 Department of Biological Chemistry and Molecular Pharmacology, Harvard University, 240 Longwood Avenue, Boston, MA 02115, USA.
* These authors contributed equally to this work.
Present address: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
To whom correspondence should be addressed. E-mail: [email protected]
