The archaeal histone-fold protein HMf organizes DNA into bona fide chromatin fibers
The archaeal histone-fold protein HMf organizes DNA into bona fide chromatin fibers
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DOI：
10.1016/s0969-2126(01)00682-7
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发表时间：
2001-12-01
期刊：
影响因子：
5.7
通讯作者：
Leuba, SH
中科院分区：
文献类型：
--
作者：
Tomschik, M;Karymov, MA;Leuba, SH
背景：在古细菌中发现组蛋白样蛋白促使研究古细菌基因组在染色质中的可能组织。尽管最近的进展，各种各样的结构问题仍然unanswered.Results：我们已经使用了原子力显微镜（AFM）与传统的核酸酶消化分析，比较串联重复的真核核细胞核小体定位序列和组蛋白八聚体，H3/H4四聚体，和组蛋白倍古菌蛋白HMF重建的核蛋白复合物的结构。这些数据明确地表明，HMf重组确实是组织为染色质纤维，在形态上与其真核对应物无法区分。核酸酶消化模式揭示了规则间隔的清晰保护模式，再次类似于真核染色质纤维观察到的模式。此外，我们研究了HMF重组单体大小的DNA片段，并观察到很大程度的相似性，这些颗粒的内部组织和那些组织的H3/H4四聚体。在单，双，和三粒子的水平上观察到的HMf颗粒和典型的八聚体含有nucleosome.Conclusions之间的稳定性的差异：在体外重建的HMf-核蛋白复合物可以被认为是真正的染色质结构。在单颗粒水平上的稳定性差异应该是由于HMf和核心组蛋白H3/H4四聚体之间的结构差异，即，HMf中组蛋白折叠以外的组蛋白尾部的完全缺失。我们推测，在真核生物中的核心组蛋白尾部的存在可能提供了一个更大的稳定性，核小体颗粒，也提供了额外的能力，染色质结构，以调节DNA功能的真核细胞中的组蛋白尾部的翻译后修饰。
Background: The discovery of histone-like proteins in Archaea urged studies into the possible organization of archaeal genomes in chromatin. Despite recent advances, a variety of structural questions remain unanswered.Results: We have used the atomic force microscope (AFM) with traditional nuclease digestion assays to compare the structure of nucleoprotein complexes reconstituted from tandemly repeated eukaryal nucleosome-positioning sequences and histone octamers, H3/H4 tetramers, and the histone-fold archaeal protein HMf. The data unequivocally show that HMf reconstitutes are indeed organized as chromatin fibers, morphologically indistinguishable from their eukaryal counterparts. The nuclease digestion patterns revealed a clear pattern of protection at regular intervals, again similar to the patterns observed with eukaryal chromatin fibers. In addition, we studied HMf reconstitutes on mononucleosome-sized DNA fragments and observed a great degree of similarity in the internal organization of these particles and those organized by H3/H4 tetramers. A difference in stability was observed at the level of mono-, di-, and triparticles between the HMf particles and canonical octamer-containing nucleosomes.Conclusions: The in vitro reconstituted HMf-nucleo-protein complexes can be considered as bona fide chromatin structures. The differences in stability at the monoparticle level should be due to structural differences between HMf and core histone H3/H4 tetramers, i.e., to the complete absence in HMf of histone tails beyond the histone fold. We speculate that the existence of core histone tails in eukaryotes may provide a greater stability to nucleosomal particles and also provide the additional ability of chromatin structure to regulate DNA function in eukaryotic cells by posttranslational histone tail modifications.