Transcription and Translation 1201 120320 RNA polymerase II

Transcription and Translation 12/01 – 12/03/20

RNA polymerase II transcriptioninitiation complex • Initiation by Pol II (get one color of CLAY) requires general transcription factors (get a different color of CLAY please), which position Pol II at initiation sites and are required for transcription of most genes transcribed by this polymerase • General transcription factors are multimeric and highly conserved • Proteins comprising the Pol II transcription-initiation complex assemble in a specific order in vitro but most of the proteins may combine to form a holoenzyme complex in vivo

Get two new colors of Clay • Color 1 = 5’ to 3’ of DNA • Color 2 = 3’ to 5’ direction of DNA • Go ahead and make your helix!

Formation of the active eukaryotic transcription initiation complex The TFIID binds to the TATA Box through its TBP subunit TFIID is stabilized by TFIIA

The conserved C-terminal domain of TATA Binding Protein (TBP) binds to TATA -box DNA TBP is a subunit of TFIID

TFIIH Te Cal in rm TATA ng i nd Bi RNA Polymerase II n ai m Do

Formation of the active eukaryotic transcription initiation complex TFIIH phosphorylates the CTD, Leading to a conformational change

Stepwise assembly of Polymerase II transcription-initiation complex in vitro For the exam, know the components of the transcriptioninitiation complex For the exam, know the components of the preinitiation complex CTD = COOH Terminal Domain

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Don’t need to know this for the exam, just appreciate that: Multiprotein complexes form on enhancers

08_10_transcr. factors. jpg How a former textbook demonstrates these series of events

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Figure 7 -8 Essential Cell Biology (© Garland Science 2010)

Table 7 -1 Essential Cell Biology (© Garland Science 2010)

Movie Time……Transcription Website: http: //www. youtube. com/watch? v=Wsof. H 466 lqk&feature=related

Transcription in Prokaryotes • There is only one type of RNA polymerase in prokaryotic cells (there are 3 RNA polymerases in eukaryotes) • The transcription complex is composed of an RNA polymerase and a sigma factor, this factor dissociates after transcription has begun • Bacterial promoters are located upstream from the site of initiation 1) 2) They have conserved regions: the -35 region and the Pribnow box The most common version of the conserved sequence is called the consensus sequence Termination can require a rho factor or be rho independent

07_09_1_bacterial gene. jpg May require rho

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Figure 7 -17 Essential Cell Biology (© Garland Science 2010)

Figure 7 -18 Essential Cell Biology (© Garland Science 2010)

Eukaryotic transcripts need further processing to leave the nucleus…

Be careful here, this is NOT an intron, it is small noncoding RNA !!! 07_12_capping. jpg

Figure 7 -16 a Essential Cell Biology (© Garland Science 2010)

Okay, eukaryotic m. RNA needs to be processed further…. Splicing time to remove introns

Figure 7 -19 Essential Cell Biology (© Garland Science 2010)

Figure 7 -20 Essential Cell Biology (© Garland Science 2010)

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For the exam, do not need to memorize the sequence of U 1 -U 6 sn. RNP additions/releases. You DO need to understand the 4 important sites in the pre-m. RNA transcript for this reaction to occur. Know that small noncoding RNAs are important functional members of the spliceosome.

Spliceosome

Movie Time: The Spliceosome http: //www. youtube. com/watch? v=FVu. Aw. BGw_p. Q And Garland Science Video to show function of sn. RNPs

For more videos please see http: //vcell. ndsu. edu/animations This is a great site showcasing many videos of the virtual cell Enjoy!!!

Translation

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What molecules are needed for translation? m. RNA Transfer RNA (t. RNA) Ribosomes A good attitude! You always need this!

Transfer RNA has a place where an amino acid attaches and an anticodon Amino acid attachment site Anticodon

Transfer RNA has a place where an amino acid attaches and an anticodon Amino acid attachment site Hydrogen bond RNA polynucleotide chain Anticodon

There is only 1 amino acid per t. RNA Amino acid attachment site Hydrogen bond RNA polynucleotide chain Anticodon

The anticodon is complimentary to the codon. Amino acid attachment site So if the anticodon is UAC, then it can only pair with a codon of AUG! Anticodon

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Each ribosome has a “P” and an “A” site. P site A site P m. RNA binding site A

Each ribosome has a “P” and an “A” site. P site Next amino acid to be added to polypeptide A site Growing polypeptide t. RNA P m. RNA binding site A m. RNA Codons

Translation consists of three steps Initiation Elongation Termination

Initiation Translation begins at the start codon on the m. RNA Start of genetic message End

Initiation m. RNA, a specific t. RNA, and the ribosome subunits assemble during initiation Large ribosomal subunit Initiator t. RNA P site A site Start codon m. RNA 1 Small ribosomal subunit 2

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Elongation

Elongation Amino acid Polypeptide A site P site Anticodon m. RNA 1 Codon recognition m. RNA movement Stop codon New peptide bond 3 Translocation 2 Peptide bond formation Figure 10. 14

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Termination

Termination

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Translation http: //www. youtube. com/watch? v=5 b. LEDd-PSTQ