Transcription In Prokaryotes PDF

The amateur practices until she gets it right. The professional practices until she cannot get it wrong.  2 PART II-A: Gene structure Transcription  3 Gene Protein coding gene:...

The amateur practices until she gets it right. The professional practices until she cannot get it wrong.  2 PART II-A: Gene structure Transcription  3 Gene Protein coding gene: Nucleotide sequence containing the information that encodes for the order of amino acids in a polypeptide. RNA gene: Nucleotide sequence that determine the order of rNTPs of an RNA molecule.  4 Prokaryotic genes have a promoter, an RNA coding region and a transcription terminator DNA sequence bound by transcription DNA segment that Templateapparatus. strand will be used Cis-acting signals where to synthesize RNA via transcription should end. Determines: transcription. Template strand Includes the transcription Direction of transcription terminator Transcription start site  5 Consensus sequences in E. coli promoters: -35 and -10 elements Pribnow box  6 Additional regulatory elements in bacterial promoters UP element: upstream element EXT: -10 extended element. DIS: discriminator. CRE: core-recognition element. Bacterial promoters rarely contain all of these elements. Consensus sequence motifs indicated below each element  7 Please fix in your textbook (p. 32) / Plus / Minus  8 Transcription in E. coli 1. Transcription initiation: Promoter recognition Formation of the closed complex Formation of the open complex 2. Transcription elongation 3. Transcription termination Intrinsic (template encoded) -or- Factor dependent  9 The sigma factor recognizes and binds the promoter consensus sequences -50 to +20  10 Sigma domain 1 prevents template access to the RNAP active site Sigma domain 2 interacts with the -10. Sigma domain 3 interacts with the EXT -10. Sigma domain 4 interacts with the -35 element. Sigma domain 2 interacts with the non-template strand at -10 causing DNA to melt so the single stranded template can enter RNAP active site. Note: image has been updated  11 Please fix in your textbook (p. 34) Sigma 4: Binds to -35 element Sigma 3: Binds to EXT element Sigma 2: Binds to -10 element Sigma 1: RNAP active site 12  13 Transcription (elongation) Abortive initiation (2-6 nt) After about ~12 nt, sigma factor dissociates 14  15 Intrinsic termination Terminator sequence: GC-rich palindrome followed by poly-A stretch on template strand. Formation of GC hairpin loop in mRNA leads to dissociation of weak U:A hybrid.  16 Factor dependent termination Rho can interact with the transcript at rut site. Travels in 5’ > 3’ Rho removes RNAP from template. tructure of the prokaryotic gene (dsDNA) Promoter + Regulatory Sequences RNA Coding Region 3' UTR (contains Transcription TTGACA TATAAT 5' UTR ORF 1 UTR ORF 2 Terminator) Up Element -35 EXT -10 Dis +1 Start Stop Start Stop Codon Codon Codon Codon tructure of the prokaryotic mRNA (ssRNA) o rn lga e a -D nc ine que Sh se ORF 1 UTR ORF 2 +1 5' UTR 3' UTR Start Stop Start Stop Codon Codon Codon Codon Note: image has been updated  18 ADDITIONAL SLIDES  19 Prokaryotic mRNA 20  21 Transcription (bacteria) 22 23  24 The DNA duplex remains double stranded and that the contacts result in sigma domain 2 being positioned adjacent to the promoter -10 element The DNA duplex around position +1 is unwound, with sigma domain 2 making specific base contacts with the single-stranded non- template strand of the promoter -10 element, thereby permitting the single- stranded template strand to enter the RNAP active site.  25 Sigma domain 3 interacts with the EXT. Sigma domain 4 interacts with the -35 element. Sigma domain 2 interacts with the non- template strand at -10 causing DNA to melt so the single strand template can enter RNAP active site.