Biochemistry Chapter 26 Flashcards
Define transcription
Making an RNA transcript of a DNA strand, using Uracil instead of Thymine.
Describe mechanisms and molecules associated with initiation of E.coli transcription
Regulated by promoter, specific region of a gene that regulates transcription of that gene
Needs: Five core and one dissociating subunit
Four NTP
Mg2+
DNA template
DNA Polymerase 1 location, cellular transcripts, and inhibition strength
In the nucleolus
Transcribes 18 S, 28 S, and 5.8 S
No inhibition
Describe specific examples, basic transcription factors, and their roles in transcription catalyzed by RNA polymerase 2
Made of 12 complex subunits
Requires additional transcription factors (TF)
Some TFs only bind specific promoter sequences and assist transcription (Ex. TF II D)
Some bind Pol 2 and assist in transcription (Ex. TF II E)
Name at least one general inhibitor of transcription and its mechanism of action
Acridine and it reduces telomerase activity
Name at least one specific inhibitor of bacterial transcription and its mechanism of action
Rifampicin inhibits DNA-dependent RNA polymerase by binding to the Beta subunit
Effective mostly against mycobacteria
Used for treating tuberculosis, leprosy, and bacterial infections
Describe three major steps during post-transcriptional processing of eukaryotic mRNA and their biological significance
5’ end capping: Multiple enzymatic steps are involved in addition of -7methyl-Guanosine cap to the primary transcript to protect it from degradation from 5’ end
Intron splicing: Systematic removal of introns and sequential re-ligation of necessary exons to form mature mRNA. Several specific enzymes and accessory proteins are required to complete this process
Poly-A addition: Polyadenylate polymerase adds 10-300 to the 3’ end of cleaved transcript without any template; Poly-A tail addition regulates the stability and/or species of an mRNA
Define reverse transcription; discuss biological and pharmacological significance of this process
Process of making DNA copy from an RNA strand
Made of two subunits
Catalyze three reactions: RNA dependent ssDNA synthesis, RNA degradation, and ssDNA dependent DNA synthesis
No proofreading activity
Important tool in basic research
Valuable pharmacological target
Describe RNA dependent DNA synthesis; discuss biological and pharmacological significance of this process
Viral RNA enters host cell
An RNA-dependent DNA polymerase called reverse transcriptase uses ssRNA as a template to synthesize ssDNA
ssRNA is destroyed and the remaining ssDNA is used as a template to synthesize dsDNA
dsDNA integrates into the host genome and replicates to form multiple viral particles
Describe RNA dependent RNA synthesis in eukaryotes and its biological significance and potential pharmacological significance
RNA viruses encode protein which replicate their RNA
Catalyzed by RNA-dependent RNA polymerase
RdRP functions with other viral and/or cellular proteins
Describe mechanisms and molecules associated with elongation of E.coli transcription
Conformational change of the transcription complex occurs
Complex moves forward and keeps moving till the synthesis of 10 nt long RNA
Needs: No extra parts from initiation
Ends: Elongated transcription complex
Describe mechanisms and molecules associated with termination of E.coli transcription
Transcription can be Rho-dependent or Rho-independent
Rho-dependent needs disruption of transcription bubble to release RNA from the complex
Rho-independent is unstable at certain sequences, so it disassembles the transcription bubble itself
DNA Polymerase 2 location, cellular transcripts, and inhibition strength
In the nucleoplasm
Transcribes mRNAs and snRNAs
Strong inhibition
DNA Polymerase 3 location, cellular transcripts, and inhibition strength
In the nucleoplasm
Transcribes tRNAs and 5 S RNAs
Inhibition at very high concentrations
RNA dependent DNA/RNA synthesis central path
DNA replication –> DNA –> Transcription –> RNA
RNA –> Reverse transcription –> DNA
