The flashcards below were created by user
Anonymous
on FreezingBlue Flashcards.
-
Transcription of RNA
- RNA polymerase binds to DNA promoter
- Polymerase synthesizes RNA based on DNA sequence
- DNA sequence signals the ends of transcription
-
An RNA sequence is same as the:
DNA Non-template "coding" strand
-
RNA transcription uses how many strands of DNA
Either
-
RNA can initiate RNA synthesis ___ and starts at a ___
de novo, promoter
-
E. coli sigma 70 holoenzyme
- Well studied RNA polymerase
- Composed of core enzyme with additional subunit called sigma, which provides initiation specificity. Core enzyme does elongation, sigma does initiate. Sigma subunits can vary
-
How many types of Eukaryotic RNA polymerase
3
-
Experimental approaches that identified promoters
- Genetics: mutations that change the
- frequency of transcription initiation
- Biochemistry: DNA sequences that initiate
- transcription by RNA polymerase
Sequence comparisons: common DNA sequences found near RNA 5’ end
Footprint assays: DNA sequences bound by RNA polymerase
-
Typical Eukaryotic promoter
TATA box
-
Prokaryotic RNA synthesis
- RNA polymerase binds DNA promoter
- Local denaturation at promoter
- RNA primer synthesis
- sigma unit released, RNA pol moves off promoter
- Polymerase synthesizes RNA based on DNA synthesis
- DNA sequence signals end of RNA transcription
-
Steps in transcription initiation
- Closed complex formation: RNA polymerase (R) binds to double stranded DNA promoter (P). R+P becomes RPc.
- Open complex formation: RPc isomerizes to form open complex in which there is a localized denaturation of DNA. Template DNA located in active site of enzyme (RPc to RPo)
- Initiation: Ribonucleoside triphosphates condensed to form short oligonucleotides complementary to template strand. (RPo + rNTPs yields short oligonucleotides +RPi)
- Promoter clearance: sigma subunit and promoter released. Core R starts extending oligonucleotides to long RNA molecule.
-
How does RNA polymerase add nucleotides
phosphoryl-transferase
-
Termination of transcription
- Intrinsic Termination (Rho-independent): A G-C rich RNA sequence forms hairpin structure, followed by UUUU which destabilizes RNA polymerase nucleoprotein complex, termination
- Rho-stimulated termination: Bacterial protein called rho, or p, terminates transcription at specific regions. Mechanism unclear.
-
Eukaryotic RNA polymerases
- Pol I, II, III
- Pol I, III: code for non-coding RNA (I: rRNA, III: tRNA, some rRNA, additonal RNAs)
- Pol II: Codes for mRNA--->ribosome--->protein
-
Eukaryotic Transcriptional Initiation requires:
Multiple Protein Components
-
Initiation factors associate dynamically with the promoter
-
Rifampin does what
- Blocks bacterial RNA polymerase, prevents release of sigma subunit and subsequent elongation
- Tuberculosis
|
|