3基因表达的调控（Regulation of gene expression）.doc

3基因表达的调控（Regulation of gene expression） Chapter iii regulation of gene expression Gene expression: the genetic information transfer process of DNA, mRNA, protein Regulation of gene expression The activation of the first gene The activation of the gene switch - chromatin The structure of the active chromatin Interphase karyochromatin: Heterochromatin, highly compressed (not transcribed); Euchromatin, relatively loose, About 10% of chromatin is active chromatin (more open and porous). The active chromatin is the non-reactive chromatin The structure characteristics of reactive chromatin (1) sensitivity of DNaseI The chromatin of transcription activity (or potentially transcriptional activity) is more sensitive to DNase I. DNase I HyperSensitive Sites (DHSS) (2) CyS110 of histone H3 was exposed to sulfhydryl. The formation of reactive chromatin structure (a), nuclear small position (Phased positioning) The rotational positioning of the nucleosomes The correlation between the core and the DNA double helix in the spatial structure of the nucleosomes, including the large groove of the DNA double helix is the orientation or the back to the core structure. 2. Translational positioning of nucleosomes The location and manner of the binding of nucleosomes and specific DNA sequences, especially the DNA regulatory elements (promoters, enhancers, etc.) associated with transcriptional activity, and the interpositional relations of the nucleosomes. (2) group protein modification H1 protein phosphorylation Promoting chromosomal packaging, affecting transcription activity, 2. Modification of core group protein Acetylation: Lys that often occur in histones, The general active chromatin is highly acetylated. (3) HMG protein binding HMG (high mobility group) protein - high mobility protein, such as HMG14 / HMG17. Combined with core particles of nucleosomes, beneficial transcription. DNA methylation and gene expression. (1) Methylation of eukaryotic genome DNA In the mammalian genome, 5%