于军课题组解析核小体基因组密码

　　

生物通报道，中科院北京基因组所研究员于军指导的博士生陈开富、孟庆姝成功对阴道滴虫基因组的核小体进行定位分析。相关成果文章发表在牛津大学出版社旗下的期刊《Nucleic Acids Research》上。

 

北京基因组所消息，陈开富、孟庆姝等所在的重点实验室阴道滴虫课题组在对阴道滴虫基因组的研究中，成功检测到一个长约121核苷酸的DNA序列周期，并证明该序列周期为核小体在基因组上的定位信号。 该课题组的研究结果表明，核小体在基因组上的结合位置并非随机分布的，一些DNA序列，尤其是基因编码区，能够长期稳定地与核小体结合，并在漫长的进化过程中优化DNA序列组分，以利于与核小体的结合。这种优化的序列组分，即可能是核小体定位的重要信号，如课题组新发现的121核苷酸长的序列周期以及过去报道的10核苷酸长的序列周期等。

 

基因组DNA的高级折叠结构及其对基因组功能的调控作用一直是科学家们关注的重要问题，亦是表观遗传学研究的一个重要方向，真核生物基因组DNA折叠成染色体高级结构的第一步是与核小体结合，其中一个关键的问题是，核小体在基因组上的结合位置是随机分布的还是由DNA编码的。

 

目前，该课题组正在以阴道滴虫为模式生物就该问题作更深入的研究，以期完全揭开定位核小体的基因组密码，以及这种定位的功能意义。

原文检索：A novel DNA sequence periodicity decodes nucleosome positioning

 

【Abstract】

There have been two types of well-characterized DNA sequence periodicities; both are found to be associated with important molecular mechanisms. One is a 3-nt periodicity corresponding to codon triplets, the other is a 10.5-nt periodicity related to the structure of DNA helixes. In the process of analyzing the genome and transcriptome of Trichomonas vaginalis, we observed a 120.9-nt periodicity along DNA sequences. Different from the 3- and 10.5-nt periodicities, this novel periodicity originates near the 5'-end of transcripts, extends along the direction of transcription, and weakens gradually along transcripts. As a result, codon usage as well as amino acid composition is constrained by this periodicity. Similar periodicities were also identified in other organisms, but with variable length associated with the length of nucleosome units. We validated this association experimentally in T. vaginalis, and demonstrated that the periodicity manifests nucleotide variations between linker-DNA and wrapping-DNA along nucleosome array. We conclude that this novel DNA sequence periodicity is a signature of nucleosome organization suggesting that nucleosomes are well-positioned with regularity, especially near the 5'-end of transcripts.