Contents Gene expression in eukaryotes Regulation on DNA level Regulation of transcription Transcription factors Regulation of gene expression by hormones and cytokines Post-transcriptional regulation Translational regulation Gene expression and development
1. Gene expression in eukaryotes Cells express about 15% of their genes Cell-specific expression: e.g. In lymphocytes ['l ɪ mfə,sa ɪ t], antibody genes are expressed at a high level.
Expression pattern can change during the lifetime of a cell: e.g. from primitive progenitor [prə ʊ 'd ʒ en ɪ tə] cells to blood cells Importance in understanding gene expression
Various levels of regulation that are possible during the expression of genetic material
反式作用元件的结构和功能： （ 1 ）概念： 反式作用元件是 DNA 结合蛋白（转录因子），可 使邻近基因开放（正调控）或关闭（负调控）。 The transcription factors are synthesized in the cytoplasm of the cell but exert their effects in the nucleus, so are called trans-acting factors. 核蛋白 （ 2 ）通用或基本转录因子 —RNA 聚合酶结合启动子所必需的 一组蛋白因子。 如： TF Ⅱ A 、 TF Ⅱ B 、 TF Ⅱ D 、 TF Ⅱ E 等。 （ 3 ）特异转录因子 ( special transcription factors)— 个别基 因转录所必需的转录因子. 如： OCT-2 ：在淋巴细胞中特异性表达，识别 Ig 基因的启动 子和增强子。
4. Transcription factors Transcription factors are a large family of proteins that regulate the expression of protein coding genes. The overall effect on transcription depends on the complement of transcription factors bound.
Transcription factors consist of discrete protein domains with specific functions. Common domains DNA binding domains DNA 结合结构域 Dimerization domains 二聚化结构域 Transactivation domains 转录激活结构域
–Basic domains. Usually found in association with one of two dimerization domains called the leucine zipper （ bZIP ） or the helix-loop-helix （ HLH ）. Binding to DNA requires the presence of two basic domains which are brought together by dimerization. Basic domain
螺旋 - 环 - 螺旋结构域 The helix-loop-helix domain ， HLH 结构域。 Two helices separated by a nonhelical loop. Dimerization by hydrophobic （疏水的） amino acids present on one side of the carboxyl terminal helix Homodimers and heterodimers: e.g. MyoD family in regulating gene expression in developing muscle cells
Transcription factors regulate the expression of target genes by binding to the transcription initiation complex and changing its stability. Some transcription factors can repress transcription either directly or indirectly
5. Regulation of gene expression by hormones and cytokines Steroid hormone （类固醇激素） : lipid- soluble, can pass through the cell membrane into the cytoplasm and bind to steroid hormone receptor, release and dimerize and translocate to the nucleus, bind promoter and activate transcription
Polypeptide hormone （多肽类激素 ） and cytokines （细胞因子） : bind receptor, signal transduction, stimulate transcription
Questions The levels of regulation of gene expression in eukaryotes. The mechanism that transcription is regulated in eukaryotes. List cis-elements and transcription factors in eukaryotes. What does post-transcriptional regulation mean?