仔猪早期断奶和母猪信息传递.ppt

不同的表遗传机制交互作用，产生各种表现型，对环境产生反应，并将获得的性状传递给下一代。在一定的条件下，这种表遗传导致的性状可以被逆转。 /RC/VL/GG/chromosome.html 染色体 染色质与核小体 DNA enters the nucleosome via interaction with the (H2A + H2B) dimer, winds twice around the two (H3 + H4) dimers forming the center of the core and then exits the nucleosome via interaction with the other (H2A + H2B) dimer as shown in the next slide…. http://tru.ca/schs/biol/facpgs/nelson/courses/bio335/notes/a335nastructure/nastruct6.html 组成: 1 四聚体 (H3-H4)2 2 二聚体 (H2a-H2b) 146 base pairs DNA 核小体和组蛋白 Nucleosome Structure without the DNA Luger, et al., Nature 389, 251-60 (1997) blue: H3; green: H4; yellow: H2A; red: H2B 组蛋白游离的氨基末端是表遗传修饰的靶点 5’ 5’ 3’ 3’ 基因表达的表遗传调控 核小体重塑 DNA 甲基化 组蛋白修饰 基于RNA的调节机制 DNA上核小体的重新配置 核小体重塑 Original observations of methylcytosine: Plants Animals: Wyatt, Nature 166 237-8 (1950) Bacteria Phage: Dunn and Smith, Nature 175 336-7 (1955) 5’ 5’ 3’ 3’ CH3 | CH3 | CH3 | CH3 | CH3 | CG CG CG CG CG CG CG CG CG CG CH3 | CH3 | CH3 | CH3 | CH3 | Cytosine Cytosine 5-Methylcytosine DNMT1 - “maintenance” methytransferase (methylates the unmethylated strand of hemimethylated DNA) DNA甲基化 Original identification of histone methylation and acetylation: Allfrey, Proc Natl Acad Sci U S A 51: 786-94 (1964) H3K27me3 = 3 methyls on lysine 27 of H3 Methylation – mono, di, trimethylation possible 组蛋白修饰 Gene activation correlated with H3-K9 acetylation Gene silencing associated with H3-K9 methylation 组蛋白修饰与转录活性的关系 H2A ~ 16 statesH2B ~ 64 statesH3 ~ 900 statesH4 ~ 120 states 每个核小体有2 x 4 个组蛋白，每个核小体所含的信息量：162 x 642 x 9002 x 1202 = 1.2x1016 每个哺乳动物细胞有 ~107 核小体 “Code” or “Language”? 组蛋白密码复杂性的计算 转录后基因沉默 (PTGS) miRNAs (~22-nt long). siRNAs = small interfering RNAs (21-23 nt long) piRNA = Piwi-interacting RNA (26-31 nt long) 转录水平基因沉默 (TGS) Same siRNAs induce DNA methylation, histone methylation, nucleosome remodeling. 基于RNA的调节机制 具有转录活性的 DNA （上） 不具有转录活性紧密的染色质（下）。 Transcriptionally active chromatin is associated with acetylated histones, wher