Transcript will bind
Regulation of gene expression Fall, 2015 1 Gene Expression Regulation in Prokaryotes it includes: • • • • • 2 Control of transcription , little on translation How much mRNA is formed How many times it is translated How stable a protein after being made Amount of functional protein which is made Operon • Structure that is unique to prok. cells • Grouping of genes with common function on the same location on DNA • One promoter make single mRNA that encodes more than one gene • More than one gene encoded on the mRNA 3 Lac operon 4 Inducible gene 5 No lactose 6 In the presence of lactose: allolactose as inducer 7 8 9 Promoter seq. of lac operon: No TATA box like 10 CAP: helps RNA pol. to bind 11 X-gal: artificial indicator 12 IPTG: Confuses lac repressor which will bind to it and prevent repressor to bind to operator 13 Tryptophan operon Attenuation: for amino acid synthesis operon, 10 genes for Trp operon. Red seq: antiterminator blue seq: terminator 14 Plenty of Trp 15 Very little of Trp 16 Several operon regions of different amino acids 17 Eukaryotic gene expression • Complex process • Governed by differentiation and histones 18 19 Nucleosomal core particle 20 Side view 21 schematic 22 Histones conservation of structure, similar structures, between and within organisims 23 supercoiling 24 DNA binding protein domain 25 Zinc fingers: portion of prot binding to DNA 26 Mediator: bridge the gap between TF and RNA plo. 27 Enhancers: sequences bound by proteins that affect transcription in a tissue specific manner 28 Transgenic chicken transformed with muscle enhancers, gene expression during development 29 Covalent modification to DNA: methylation if happened in promoter or regulatory sequence tends to silence the gene, methylation is an example of epigenetic transmitting to generations 30 Hormones could affect gene expression. Esradiol affects expression of many genes 31 Mechanism of action of estradiol: interacts with Nuclear Domain Receptor protein which has 2 domains; DNA binding domain and ligand binding domain which estradiol 32 33 34 Tamoxifen interferes with the action of estradiol, it binds the nuclear receptor and thus inhibit binding of coactivator 35 36 Coactivators are enzymes that acetylate histones(Histone acetylases) 37 Bromo domain proteins will recognize acetyllysine, so these bromodomain proteins will bind to histones; remodeling engine 38 Remodeling engine opens up access to promoter to all other proteins and transcription factors 39 Control of expression at translation level: -ferritin: binds to iron -transferrin receptor: controls how much iron gets in. control at translation and stability of mRNA 40 mRNA for ferritin -iron response element: This structure is a target to a protein that recognize it- iron response protein (IRP), IRP could bind iron at high iron level. -At low iron level: IRP bind IRE and prevents translation of ferr. mRNA -if high iron level: translation will go a head? 41 mRNA transferrin receptor: -low iron: IRP binds and stabilizes the mRNA high translation -high iron: IRP will not bind IRE, mRNA will be degraded no translation 42 Micro RNA: Regulation at the level of mRNA stability 700 human genes are regulated by this mechanism 43