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Gene Expression M.Tevfik DORAK http://www.dorak.info. DNA double helix (2-nm diameter). Histones. “Beads on a string”. Nucleosome (10-nm diameter). Tight helical fiber (30-nm diameter). Supercoil (200-nm diameter). 700 nm. Campbell NE et al (Eds): Biology: Concepts & Connections
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Gene Expression M.Tevfik DORAK http://www.dorak.info
DNAdoublehelix(2-nmdiameter) Histones “Beads ona string” Nucleosome(10-nm diameter) Tight helical fiber(30-nm diameter) Supercoil(200-nm diameter) 700nm Campbell NE et al (Eds): Biology: Concepts & Connections 4th Edition, 2003 Metaphase chromosome
Idea: measure the amount of mRNA to see which genes are being expressedin (used by) the cell. Measuring protein might be better, but is currently harder. Gene expression does not always result in a protein product !
Medical Biochemistry Pages http://www.indstate.edu/thcme/mwking/gene-regulation.html
Expression of the human b-globin gene. Exons 1 and 3 each contain noncoding sequences (shaded bars) at their extremities, which are transcribed and are present at the 5’ and 3’ ends of the b-globin mRNA, but are not translated to specify polypeptide synthesis. Such 5’ and 3’ untranslated regions (5’ UTR and 3’ UTR), however, are thought to be important in ensuring high efficiency of translation. The stop codon UAA represents the first three nucleotides of the 3’ untranslated region. Note that the initial translation product has 147 amino acids, but that the N-terminal methionine is removed by post-translational processing to generate the mature b-globin polypeptide. From: Human Molecular Genetics by Strachan & Read. NCBI Books Online
From: Principles of Molecular Medicine. LL Jameson (Ed). Humana Press, 1998
University of Arizona Biology Project http://www.biology.arizona.edu/molecular_bio/molecular_bio.html
Enhancers Promoter Gene DNA Activatorproteins Transcriptionfactors Otherproteins RNA polymerase Bendingof DNA Transcription Complex assemblies of proteins control eukaryotic transcription A variety of regulatory proteins interact with DNA and each other Campbell NE et al (Eds): Biology: Concepts & Connections 4th Edition, 2003
Chromosome DNA unpackingOther changes to DNA GENE TRANSCRIPTION GENE Exon RNA transcript Intron Addition of cap and tail Splicing Tail Cap mRNA in nucleus NUCLEUS Flowthroughnuclear envelope mRNA in cytoplasm CYTOPLASM Breakdown of mRNA Translation Broken-down mRNA Polypeptide Cleavage/modification/activation ACTIVE PROTEIN Breakdownof protein Broken-down protein Campbell NE et al (Eds): Biology: Concepts & Connections 4th Edition, 2003
A eukaryotic promoter: This promoter contains three promoter elements upstream of the TATA box that are required for efficient transcription: a CCAAT box and two GC boxes (consensus sequence GGGCGG). From: The Cell by GM Cooper. NCBI Online Books
Morey AK et al. JBC 1998 (http://www.biochemj.org/bj/330/1097/3301097.pdf) Chromosomal Location: 6p21.4 EDN1 Locus: ID 1906 EDN1 Genome Annotation (chromosome 6 reference genomic contig) : NT_007592 EDN1 Genomic Sequence (including the promoter region): J05005
EDN1 (GeneID 1906) GI: 340555 repeat_region 98...383 /rpt_family="Alu" protein_bind 739...745 /bound_moiety="acute phase reactant regulatory element" misc_feature 979..1039 /note="Z-DNA region; putative" protein_bind 2183..2188 /bound_moiety="acute phase reactant regulatory element" protein_bind 2951..2958 /bound_moiety="TPA/JUN" protein_bind 3241..3248 /bound_moiety="TPA/JUN" protein_bind 3316..3328 /bound_moiety="NF-1" protein_bind 3499..3505 /bound_moiety="TPA/JUN" CAAT_signal 3510..3515 /gene="EDN1" TATA_signal 3577..3582 /gene="EDN1" Exon 1 3608..3939 /gene="EDN1"
Medical Biochemistry Pages http://www.indstate.edu/thcme/mwking/rna.html
Generating Protein Diversity from the “Small” Human Genome Alternative Splicing Can Generate Very Large Numbers of Related Proteins From a Single Gene Exon 4 12 alternatives Exon 8 48 alternatives Exon 9 33 alternatives Exon 17 2 alternatives DSCAM gene and pre-mRNA splicing mRNA 38,016 12 X 48 X 33 X 2 = alternative mRNAs 49 of 50 cDNAs sequenced showed alternative splicing suggesting thousands of different proteins from the same gene. Black, Cell 103: 367, 2000
Gene Expression in Prokaryotes Glick and Pasternak Fig. 3.10
Three kinds of RNA mRNA: a copy of the gene; is translated to make protein. tRNA: smallest RNA, does actual decoding. mRNA tRNA rRNA: 3 sizes that, along with proteins, make up a ribosome rRNA http://www.cu.lu/labext/rcms/cppe/traducti/tjpeg/trna.jpeg; Tobin and Duschek, Asking About Life; http://www.tokyo-ed.ac.jp/genet/mutation/nort.gif
From: Principles of Molecular Medicine. LL Jameson (Ed). Humana Press, 1998