Replication, Transcription, Protein Synthesis Flashcards
DNA polymerase
replication
RNA polymerase
transcription
Ribosomes
translation
Replication
semi conservative
half old and half new
continuous and Okazaki fragments
template directed synthesis 5’–>3’
Replication Mismatch Repair
older strand is methylated
unmarked strand with error is corrected
segment around mutation is excised and replaced by DNA polymerase
Transcription
template-directed synthesis 5’–>3’
Not continuous like Replication
Transcription Initiation Complex
multi-protein complex built upstream of Promoter
Transcription factos recognize specific DNA sequences proximal and distal
DNA bends/loops for protein - protein interaction
complex recruits RNA Polymerase II
Enhancers/Regulatory sequences
bind proteins to attract or block RNA polymerase
Promoters
binding site for RNA polymerase
start site for transcription
Terminator
sequence site that causes RNA polymerase to fall off
Eukaryotic Transcription complex
Core Promoter contains TATA sequence that binds TFs
Proximal elements - bind specific factors
Distal elements - bind TFs, enhancers- activators, hormone response elements
Co-Activation Complex- does not bind to DNA, protein-protein interaction
RNA polymerase II- recruited + disengage cts
complex stays bound during multiple rounds of initiation
Bacteria - transcription and translation
coupling/linked
both occurs in cytoplasm
protein synthesis begins before gene transcription is completed
very fast gene expression response
Genes can be switched on to adapt to new nutrients
Glucose –> Lactose
once glucose is depleted
genes for lactose digestion is turned on to use lactose for energy
Diauxic growth
beta-galactodase cleaves lactose –> glucose + galactose
Eukaryotes- Transcription and Translation
Transcription in Nucleus
mature mRNA transported thru nuclear pores
Translation in cytoplasm
mature mRNA binds Translation factors and Ribosomes
Eukaryotes initial RNA transcript is processed
5’ end capped m7GpppG
3’ end cleaved and polyadenylated
introns spliced
Eukaryotic Translation components
"protein synthesis" energetically costly- GTP /ATP mRNA - codon tRNA- charged with AA, anticodon ribosome- catalyzes peptide bond formation Translation factors - eIFs
Eukaryotic Translation Initiation
eIF-GTP recruits
40S binds to mRNA
60S binds now forming 80S ribosome
Met-tRNA binds to P site (AUG)
Eukaryotic Translation Elongation
eEF1-GTP-tRNA A site for second charged tRNA peptidyl transfer catalyzed by 28S rRNA unit 80S ribosome moves 3nt (1 codon) 1 GTP- hydrolysis for delivery 1 GTP- translocation uncharged tRNA moves over to E site and P site opening A site
Eukaryotic Translation Termination
Release Factors (RFs) recognize stop codon in A site
eRF1 stimulates ribosome to catalyze peptidyl transfer but no AA is present for stop codons
Water - nucleophilic attack => hydrolyzes peptide chain from tRNA and release protein
other RFs causes dissociation translation complex
Tetracycline
antibiotic
binds to A site of 30S
reversibile
Erythromycin
antibiotic
blocks peptidyl transferase activity in 50S subunit
Chloramphenicol
antibiotic
blocks aminoacyl-tRNA binding to 50S
can also inhibit Euk mito translation
Streptomycin, Neoycin, Gentamycin
antibiotic
bind to 30S subunit
causes codon misreading
nonfunctional proteins
Diptheria toxin
euk translation toxin
ADP ribosylates eEF2 to block 80S translocation
prevents translocation of peptide chain from A site to P site
uses NAD+
