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transcription - Coggle Diagram
transcription
Common Features of Promoters in E. Coli
An A-T−rich upstream promoter element between −40 and
−60 binds the σ subunit
• A-T−rich sequences promote strand separaƟon
There are two consensus sequences at −10 (TATAAT) and
−35 (TTGACA) for σ subunit binding : TATA sequences
These sequences govern efficacy of RNA Pol binding and
therefore affect gene-expression level
Overview of RNA Function
Ribonucleic acids play several less-understood functions in
eukaryotic cells
– MicroRNAs
Ribozyme
Ribonucleic acids act as genomic material in viruses
Ribonucleic acids play three well-understood roles in living
cells
tRNAs
rRNAs
mRNAs
Overview of RNA Metabolism
Ribozymes
Processing of mRNAs
Poly-adenylation of the 3’ end
Splicing
Capping the 5’ end
7-methylguanosine links to 5’-
end
Protects RNA from nucleases
Forms a binding site for ribosome
Transcribed from DNA
RNA Polymerase
RNA Polymerase Is a Large Enzyme with
No Proofreading Capability
RNA Pol lacks 3’ to 5’-
exonuclease
RNA polymerase holoenzyme
has five core subunits
Eukaryotes RNA Polymerases
RNA polymerase I~ IV
Mitochondria
Assembly of RNA Polymerase II at Promoter
Initiation of Transcription
An open complex forms
RNA Pol moves away from the promoter
RNA Pol binds to promoter
intron
tRNA introns
protein-based enzymes
Spliceosomal introns
enormous complexes called
spliceosomes
Group I and group II
self-splicing
mRNA Processing
Processing of tRNA and rRNA
Addition of the Poly(A) Tail
others
The Footprinting Technique Is a Way to Find
a DNA-Binding Site
Ribozymes Are RNA Molecules That
Catalytically Cleave RNA
Elongation of Transcription
RNA Pol binds to triphosphate nucleosides and
generates the RNA transcript
NusG binds to both the RNA polymerasee and
ribosome
Regulation of Transcription
regulate gene production
egulate the affinity of RNA polymerase for
a promoter
Two Types of Termination in E. Coli
rho-independent (form a hairpin)
rho-dependent