2016染色质研究技术知识与原理.ppt

染色质研究原理与技术;一、染色质和核小体 二、DNA甲基化修饰和组蛋白修饰 三、研究染色质修饰的技术 四、体外染色质重组;染色质研究的历史性成果;A. Interphase chromatin;A) 30 nm fibers B) beads on a string-nucleosome From interphase nucleus;Chromatin digestion with MNase;Nucleosome core particle;Histones- highly basic (+) proteins;Histone fold- 3 alpha helices and 2 folds;Histone self-assembly;Nucleosome;Nucleosome;The Nucleosome;Different states of chromatin;Function Storage of genetic information（储存） Precise segregation of replicated DNA into two daughter cells（精确分离到不同） Platform for transcription, replication, recombination and DNA repair（平台） ; 二、DNA甲基化修饰和组蛋白修饰 三、研究染色质修饰的技术 ;如何进行调控？;1. 不能降解DNA或者组蛋白 2. 通过化学修饰调控 DNA甲基化，组蛋白修饰 3. 通过改变结构调控 更换不同类型组蛋白 通过ATP依赖性重塑酶改变结构;DNA methylation histone variants ATP-driven chromatin remodeling complexes Histone modifications Non-coding RNAs ;DNA Methylation;Fig. 2. A genomic region of 40 000 bases from chromosome 1 is shown. The ticks on the?x-axis represent CpG locations. The points represent CpG rates in segments of length 256 bases The curve is the result of a kernel smoother of the points. Approximately 20% of the genome are Cs and 20% are Gs. Thus, we expect about 4% of dinucleotides to be CpG. However, most points are well below rates 4% with 2 clusters well above 4%. The latter are CGI.;General function of DNA methylation;;Mammalian DNMTs (DNA 甲基化酶）;Jones and Liang, Nature Review 2009;DNA Methylation and Cancer DNA甲基化异常与肿瘤的关系;Is DNA hypomethylation a causal factor for tumorigenesis? DNA 低甲基化是否可以导致肿瘤发生？;Nature Genetics 2011;Diseases associated with abnormal methylation;ＤＮＡ甲基化酶敲除小鼠表型;　CpG methylation – how does it affect transcription? CpG methylation prevents binding of some transcription factors (SP1) Allow binding of methylated-DNA binding proteins (MBP such as MeCP2 ) MeCP2 recruits a complex of histone deacetylases and SIN3A induces a closed chromatin structure → gene silencing long term repression;Methylcytosine-binding proteins (DNA methylation readers), includ