生物文献汇报

生理影响
1.Shyhchang , et al. Cell Stem Cell, 2013. 12(4), 395.
背景
• One study in C. elegans also suggested binding of Lin28A to the let-7 genomic locus.[2] • Structurally, Lin28A is composed of two classical nucleic acid binding domains. Notably, CSD domains in other molecules have been shown to bind DNA[3] • Ten-eleven translocation (Tet) family proteins can sequentially convert 5-methylcytosine (5mC ) to 5hydroxymethylcytosine (5hmC), leading to DNA demethylation [4]
Lin28A Binds Active Promoters and Recruits Tet1 to Regulate Gene Expression
报告人：倪瑞栋
Molecular Cell, 61(1), 153-160. IF: 13.958
摘要 背景
实验
总结 个人观点
背景[1]
核心功能介绍
(co-IP)
实验
• Step 3：Lin28A Forms a Complex with Tet1 to Recruit Tet1 to Their Genomic Co-targets
图9：Bub bubble DNA更优结合Lin28A，GST（谷胱甘肽巯基转移酶）为对照组
考虑到Lin28A拥有结合DNA和RNA的能力、结合空腔，设计不同类型DNA， 得到Bub bubble DNA结合能力最优。
Over 95% of up- or downregulated genes bound by Lin28A were also bound by Tet1 on promoters or intra-genic regions
结果
实验
• Step 4：Lin28A Coordinates with Tet1 to Regulate Cytosine Modification Dynamics and Gene Expression
图10：Lin28A和Tet1密切联系
图11：证实Lin28A征募Tet1达到 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC)效果
背景[1]
生理影响 核心功能介绍
实验
• Step 1：Lin28A Binds to Specific Genomic Loci in Mouse ESCs and Directly Binds DNA
图1：ChIP集中TSS
图2：ChIP得到Lin28A结合motif 图3：EMSA证实motif与Lin28A结合
图7：Tet1与Lin28A各自DNA结合 区有5632个相同基因位点
实验
• Step 3：Lin28A Forms a Complex with Tet1 to Recruit Tet1 to Their Genomic Co-targets
图8：无论敲低Lin28A还是Tet1都会导致另外一个蛋白质富集DNA能力下降
2.Van Wynsberghe P M, et al. Nature Structural & Molecular Biology, 2011, 18(3):302. 3.Hudson, W.H., and Ortlund, E.A. Nat. Rev. Mol. Cell Biol, 2014,15, 749–760. 4. Yao, B , et al. Hum. Mol. Genet, 2014, 23, 1095–1107.
图9：Pol II酶抑制剂（Triptolide简写tri）使得Lin28A结合DNA能力下降
考虑到Lin28A与Pol II酶有相似的DNA结合区。暗示着DNA先结合Pol II，再结合 Lin28A。 Co-immunoprecipitation (co-IP) analysis免疫共沉淀
实验
说明：冷探针（cold probe），没有生物素（Biotin）标记的DNA，实验中不显色
实验
• Step 2：Lin28A Is Primarily Associated with Transcribed Genes in mESCs
图6：Lin28A敲低 （ lentivirus-mediated shRNA ）再进行RNA-seq。 用qPCR证明敲低操作是成功的。有许多基因是和DNA在ChIP实验中 是结合的，证实Lin28A确实调控基因表达（区别于直接作用RNA）。
Lin28A KD(敲低) decreased Tet1 enrichment on common targetsby30%–60%. 研究Lin28A和Tet1和DNA的结合关系，发现二者有密切联系。但敲低Tet1 不影响Lin28A与DNA结合能力
实验
• Step 3：Lin28A Forms a Complex with Tet1 to Recruit Tet1 to Their Genomic Co-targets
实验
• Step 2：Lin28A Is Primarily Associated with Transcribed Genes in mESCs
Leabharlann Baidu
图4：Lin28A与Pol II ChIP结果有重合
图5：组蛋白分析得到Lin28A结合的位点
实验
• Step 3：Lin28A Forms a Complex with Tet1 to Recruit Tet1 to Their Genomic Co-targets We compared genome-wide Lin28A distribution with published databases. Interestingly, more than half (49.1%–71.5%) of Lin28A binding sites were shared by Tet1 in mESCs.