5 mRNA Processing and Transcriptional Regulation

5 mRNA Processing and Transcriptional Regulation -...

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mRNA Processing and  Transcriptional Regulation Covering  Chapters 7 & 8 Alberts et al. 2014
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Genome Organization and Functional Relationship Genome Organization and Functional Relationship     of DNA/RNA with Nuclear Structure of DNA/RNA with Nuclear Structure
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How is RNA unique from DNA?
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2’-OH (H donor & acceptor) gives RNA > flexibility vs DNA  to create stable  3D complex conformations
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RNA Higher Order Structures Possible due to the unique base-pairing occurring throughout the molecule to form hairpin loops, internal or stem-loops and tertiary  folding structures like clover leaf  or pseudo knots.
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RNA Synthesis Run By RNA Polymerase RNA Synthesis Run By RNA Polymerase RNA Pol unlike  DNA Pol does not need a primer to begin
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Prokaryotic Gene Transcription with RNA Polymerase Initiation Elongation Termination Sigma Factor : Sigma Factor : a subunit of  RNA polymerase  which provides  DNA binding  specificity to the  promoter and aids start of  RNA transcription Closed complex Open complex Transcribing complex Complex cleared promotor
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RNA Polymerase recognizes specific promotor & terminator sequences Prokaryotes use the polarity of their promotor sequences to help determine which DNA  strand is transcribed.  When a sequence of DNA is encountered with a terminator sequence DNA transcription is halted. Regions made into DNA contain terminator but not promotor sequences
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Direction of Transcription Can Vary Gene to Gene  on Same Chromosome Gene a used bottom strand as the DNA template Gene b used top strand as the DNA template RNA Pol only moves in  RNA Pol only moves in  3’ to 5’ direction 3’ to 5’ direction
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No processing of mRNA in Prokaryotes
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15 Prokaryotic transcription is coupled to translation Notice the polyribosomes, aka polysomes
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Figure 1. The Mammalian Interphase Nucleus Shiels C, Adams NM, Islam SA, Stephens DA, et al. (2007) Quantitative Analysis of Cell Nucleus Organisation. PLoS Comput Biol 3(7): e138. doi:10.1371/journal.pcbi.0030138 rRNA genes Splicing Occurs here New Pre-MRNA Other nuclear  bodies sites of mRNA  processing
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Eukaryotes unlike Prokaryotes DO   process their pre-mRNAs to create mature mRNAs :      1. Add 5’ Cap      2. Undergo Splicing      3. Add 3’Poly A Tail      4. Export mRNA to  cytoplasm      5. Undergo RNA turnover
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