生物化学与分子生物学学习课件：基因表达调控1.pptVIP

* * * * * （二）蛋白质分子结合于启动序列或启动序列周围进行自我调节 调节蛋白结合mRNA靶位点，阻止核蛋白体识别翻译起始区，从而阻断翻译。 调节蛋白一般作用于自身mRNA，抑制自身的合成，称自我控制(autogenous control)。 （三）翻译阻遏利用蛋白质与自身mRNA的结合实现对翻译起始的调控 编码区的起始点可与调节分子（蛋白质或RNA）直接或间接地结合来决定翻译起始 调节蛋白可以结合到起始密码子上，阻断与核糖体的结合 （四）反义RNA结合mRNA翻译起始部位的互补序列对翻译进行调节 可调节基因表达的RNA称为调节RNA。 细菌中含有与特定mRNA翻译起始部位互补的RNA，通过与mRNA杂交阻断30S小亚基对起始密码子的识别及与SD序列的结合，抑制翻译起始。这种调节称为反义控制(antisense control)。 （五）mRNA密码子的编码频率影响翻译速度 当基因中的密码子是常用密码子时，mRNA的翻译速度快，反之，mRNA的翻译速度慢。 Codon-usage bias: The translation efficiency of a codon is related to the relative quantity of tRNA molecules that recognize the particular codon. * * * * * * * * * * * * * Figure 18.6 Stages in gene expression that can be regulated in eukaryotic cells * Figure 18.6 Stages in gene expression that can be regulated in eukaryotic cells * Stages in gene expression that can be regulated in eukaryotic cells * * Many maternal effect Drosophila mutants have been found that affect the early steps in embryogenesis such as axis determination, including bicoid, dorsal, gurken and oskar.[6][7][8] For example, embryos from homozygous bicoid mothers fail to produce head and thorax structures. Once the gene that is disrupted in the bicoid mutant was identified, it was shown that bicoid mRNA is transcribed in the nurse cells and then relocalized to the oocyte.[9] Other maternal effect mutants either affect products that are similarly produced in the nurse cells and act in the oocyte, or parts of the transportation machinery that are required for this relocalization.[10] Since these genes are expressed in the (maternal) nurse cells and not in the oocyte or fertilised embryo, the maternal genotype determines whether they can function. * * * * * * * * * * mRNA in cytoplasm Translation CYTOPLASM Degradation of mRNA Protein processing Polypeptide Active protein Cellular function Transport to cellular destination Degradation of protein 六、基因表达调控为生物体生长、发育的基础 Prokaryotic organisms regulate gene expression in response to their environment. Eukaryotic cells