Epigenetics and Disease Flashcards
what is the major DNA modification in mammals
5 methyl cytosine (5mC)
where a methyl group is added to a cytosine
what are the features of 5mC
essential for mammalian development
repressive to transcription
generally occurs in CpG context - has to be next to a guanine
what % of CpG’s are methylated
60-80%
what is the difference between De Novo Methyl Transferase (DNMT)3A/B
and DNMT1
DNMT3A/B methylates unmethylated DNA
DNMT1 methylates hemi-methylated DNA
what is the only epigenetic modification that has shown to be highly heritable
DNA methylation
what happens with a lack of DNMT1
gradual passive demethylation over progeny
function of TET
hydroxylates the methyl group into a hydroxymehtyl-group (OH-CH2-)
5hmC
what are the function of histone tails
extend out from core of the nucleosome
subject to post-translational modifications
what are the main types of post-translational modification histone tails are subject to
phosphorylation
methylation
ubiquitination
acetylation
function of reader proteins
recognise specific modifications
mediate downstream processes
often linked to human diseases
how is nucleosome re-modelling via sliding useful
if there is a specific region of DNA on the nucleosome - it cannot be accessed
DNA is slid along until the region is off the nucleosome
accessible to binding proteins
what are the other ways in which nucleosome re-modelling can occur
nucleosome ejection - removal of the nucleosome
H2A-H2B dimer ejection - removal of the top/bottom sections of the nucleosome
H2A-H2B dimer replacement - replacement of the top and bottom section of the nucleosome
what is general purpose of chromatin re-modelling
create region with no nucleosomes for transcription to occur
what do the end of 5’ gene re modelers all generate
a stereotypic nucleosome organisation required for transcription
what are the molecular features of enhancers
accessible DNA
histone modification
transcribed
proximal in 3D space to gene
