9 Transcription Chapters 26 Lehninger 5 th Edition

• Transcription • DNA -> RNA • Translation • RNA -> Protein

Genes • 1 gene -> 1 protein? • Transcription – Read a gene from

Transcription • RNA Polymerase – Reads DNA • Makes RNA copy of – One

Transcription • Open DNA at promoter • Make RNA – 5’-> 3’ – transcription

Transcription • Initiation – At promoters – Control by Transcription Factors – “Gene expression”

Bacterial Promoters • Simple • Fixed spacing of binding sites • Transcription factors

Bacterial Gene Structure • Simple promoter close to start of transcript • Gene transcribed

Bacterial Operons • Genes may be grouped in Operons • Co-regulation • Single transcript

Eukaryotic Gene Structure • V. complicated promoters – e. g. Human: • 2000 TFs

Eukaryotic gene processing • Remove introns – Splicing • Add 5’ cap • Cleavage

Alternative transcripts • Alternative poly. A sites • Alternative splicing – Alternative exons •

RNA Genome? • Central dogma: – DNA -> RNA -> protein • RNA Virus

What Controls Gene Expression? • Transcription factors • Regulatory RNAs – mi. RNA –

Transcription Factors • Proteins which bind DNA • Enhance or repress gene expression –

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9. Transcription Chapters 26 Lehninger 5 th Edition http: //www. steve. gb. com/science/transcription. html

• Transcription • DNA -> RNA • Translation • RNA -> Protein

Genes • 1 gene -> 1 protein? • Transcription – Read a gene from the DNA – DNA -> RNA • Translation – Translate the DNA code to protein code – RNA -> Protein

Transcription • RNA Polymerase – Reads DNA • Makes RNA copy of – One strand – One gene

Transcription • Open DNA at promoter • Make RNA – 5’-> 3’ – transcription bubble • Moves along gene – Prevent DNA knotting • DNA topo-isomerases

Transcription • Initiation – At promoters – Control by Transcription Factors – “Gene expression” • Termination • Processing of the transcript (Eukaryotes) – e. g. remove introns, add stuff to ends, modify bases • Final product – e. g. mature m. RNA or mature mi. RNA

Bacterial Promoters • Simple • Fixed spacing of binding sites • Transcription factors

Transcription Factors Bind DNA

Bacterial Gene Structure • Simple promoter close to start of transcript • Gene transcribed as one piece of m. RNA • Transcription terminates – Terminator signal • Ready to translate m

Bacterial Operons • Genes may be grouped in Operons • Co-regulation • Single transcript

Eukaryotic Gene Structure • V. complicated promoters – e. g. Human: • 2000 TFs • Spread over 10 s of kb • Several kb from coding region • Pieces of m. RNA removed before translation – Introns • Rich Roberts, Phil Sharp

Eukaryotic gene processing • Remove introns – Splicing • Add 5’ cap • Cleavage of 3’ end of m. RNA at poly. A site • Add 3’ poly. A tail

Alternative transcripts • Alternative poly. A sites • Alternative splicing – Alternative exons • Alternative promoters

Alternative poly. A

Alternative splicing

RNA Genome? • Central dogma: – DNA -> RNA -> protein • RNA Virus – e. g. HIV: • RNA -> DNA • Reverse transcriptase

What Controls Gene Expression? • Transcription factors • Regulatory RNAs – mi. RNA – sm. RNA – si. RNA • Methylation • Chromatin

Transcription Factors • Proteins which bind DNA • Enhance or repress gene expression – Families e. g. : • Homeodomain (Hox) • POU domain (Oct-1) • Helix-loop-Helix (c-Myc) • Zinc Fingers (TFIIIA) • Leucine Zipper (c/EBP) • Winged Helix (Fox family) • Helix Turn Helix • At least 10% of genes in Human genome are TFs