Transcription in prokaryotes and eukaryotes

Where does transcription happen in prokaryotes and eukaryotes?

Pro: in the cytosol due to a lack of nuclear envelope

Euk: in the nucleus

What are the RNA polymerase enzymes in prokaryotes and eukaryotes?

Pro: a single RNA polymerase produces all types of RNA, it uses a sigma factor to recognise promoters

Euk: 3 different polymerases, each have their own GTF for promoter recognition and initiation. RNA pol 2 is for mRNA

Where does transcription happen in prokaryotes and eukaryotes?

Pro: in the cytosol due to a lack of nuclear envelope

Euk: in the nucleus

What are the RNA polymerase enzymes in prokaryotes and eukaryotes?

Pro: a single RNA polymerase produces all types of RNA, it uses a sigma factor to recognise promoters

Euk: 3 different polymerases, each have their own GTF for promoter recognition and initiation. RNA pol 2 is for mRNA

Describe promoter structures and ininitaiton in prokaryotes and eukaryotes?

Pro: Conserved regions, 10-35 bases upstream of the transcription start site. RNA ;polymerase binds directly to the DNA, this is aided by the sigma factor. Smple regulation by regulators/activatiors that bind near the promoter

Euk: More complex conserved TATA box. Additional enhancers, silencers and initiators are used to regulate transcription. Polymerase 2 is recruited through a preinitation complex, this involves many proteins. Also regulated by chromatin structure, specific TFs, coactivators and repressors

Describe elongation of transcription in prokaryotes and eukaryotes?

Pro: DNA is unwound locally, ahead of RNA polymerase and rebound behind it

Euk: Chromatin remodelling complexes and histone modifications aid DNA access.

Describe termination of transcription in prokaryotes and eukaryotes?

Pro: they use two different mechanisms. Intrinsic terminator sequences mean that a GC rich hairpin loop followed vt a U rich site is present. This causes dissociation. Rho dependent termination is when Rho binds to a rut site, it uses ATP hydrolysis to move in the 5’ to 3’ direction, disrupting the RNA-DNA hybrid and causing dissociation, it can also hit polymerase off

Euk: More complex and less understood. Cleavage downstream of the PolyA tail occurs after recruitment of CPSF factors

Describe RNA processing in prokaryotes and eukaryotes?

Pro: Minimal processing

Euk: Extensive processing top modify mRNA stability. 5’ 7methylguanosine cap, 3’ polyadenylation, splicing and exon skipping. All ensure stability and nuclear export efficiency

Describe chromatin and epigenetic regulation in prokaryotes and eukaryotes?

Pro: Naked DNA, lacks chromatics, regulation is dependent on access to promoter

Euk: Histone acetylation/methylation and DNA methylation all affect transcription