DNA translation/post translation modification

central dogma

replication - transcription - translation

function of tRNA

brings the amino acids to the ribosomes

chambers of the ribosomes

E,P,A

function of E binding site

Exit site, where the empty tRNA leaves the ribosome

function of A binding site

Aminoaycl binding site, where the tRNA with amino acid enters and binds to the matching nucleotides

function of P binding site

peptidyl binding site, holds the tRNA attached to the growing polypeptide chain to attached the new amino acid

three stages of translation

initiation, elongation, termination

what is initiation

finding the start codon, binding the first amino acylated tRNA to the P site, DIFFERENT between euk and prok

what does initiation require

initiation factors

what is elongation

moving down the mRNA, binding of amino acylated tRNA to the A site, making peptide bonds

what does elongation require

elongation factors

what is termination

releasing the completed polypeptide, disassociation of the mRNA with the ribosome

where do initiation factors bind to eukaryotic mRNA

poly-A tail and 5’ cap

what forms the peptide bonds

rRNA catalyzes between aa on tRNA in P site and aa on tRNA on A site

what happens during termination

release factor binds to A site, hydrolysis cleaves bond between tRNA in P site and the polypeptide, tRNAs and ribosomes leave the mRNA

major difference of gene expression in prokaryotic vs eukaryotic cells

prok don’t have organelles, everything happens in cytoplasm, transcription and translation can happen at the same time

what is chromatin

DNA and associated proteins

what is a nucleosome

DNA wrapped around proteins called histones

what modifications can be done to histones

methylation, acetylation, phosphorylation, ubiquitination, isomerization

what does acetylation do

attaches acetyl groups to the histones, decondenses the chromatin

what does methylation do

prevents the transcription factors from binding to the promoter, stops transcription

why would the histones of a region be acetylated/methylated

acetylated if they contained a promoter/important gene for expression, methylated if not important for txn (silenced)

where are acetyl groups added

on positive charges on Lys in histones

what are HATs

Histone acetylases, add acetyl groups

what are HDACs

histone deacetylases, remove acetyl groups

where are methyl groups added

cytosine, often at CpG sites

what do activators do

recruit chromatin remodelers (HATs) that decondense the chromatin

what purpose do enhancers serve

landing pads for the activators, increase transcription

what is the proximal promoter elements

recruit regulatory proteins (activators/repressors) that are gene specific

where are silencers and enhancers

far away from the promoter sequence

what binds to silencers

repressors

why are enhancers and silencers often far away from promoters

efficiency, they can regulate multiple genes

what are ESE/ISE

exon/intron splicing enhancers, recruit snRNPs, leads to inclusion of nearby exon

what are ESS/ISS

exon/intron splicing silencers, block snRNP association, leads to exclusion of nearby exon