L9 Epigenetics Flashcards
Define epigenetics
What explains the different development and function of similar cells
mechanisms outside the direct genetic code which influence gene expression
How does chromatin play a role in epigenetics
through histone modifications, nucleosome positioning, histone variants, and DNA modification
What are epigenetic traits
stably heritable phenotypes resulting from changes in a chromosome without alterations in DNA sequence
What are examples of biological phenomena that are attributed to epigenetics
development of embryo, coat color in calico cats
Why are post translational modifications important for histones
act as signals during regulation; modifications can prevent or facilitate the recruitment of specific proteins to the chromatin
Why are histone tails important
Why are they are not observed in crystal structures
they are not ordered and interact with other nucleosomes to help compact the DNA further
What is the effect of side chain modification in the globular regions of histones
they can directly affect the chromatin structure
What does phosphorylation do to histones
(ser, thr, thy); addition of a negative charge; repulsion
What does acetylation do to histones
(to Lys) eliminates the positive charge; loss of association on DNA; DNA is more accessible
What does methylation do to histones
(to Lys, Arg) regulates interactions; methyl must be recognized by other proteins
What does ubiquination do to histones
(to Lys) regulates interactions, targets for degradation
Which proteins are considered writers
acetylases, methylases, kinases
Which proteins are considered erasers
deacetylases, demethylases, phosphatases
Which proteins are considered readers
bromodomain and chromodomain proteins, PHD finger, WD40 repeats
What do histone acetyltransferases do
add acetyl groups to lysine side chains using acetyl-coa; HDACs do the opposite
What do histone methyltransferases do
add methyl groups to lysine and arginine; demethylases do the opposite
what chromatin is more heavily acetylated
euchromatin; it is associated with active transport
what does acetylation do
removes the positive charge from lysine side chains, which affects interactions with negatively charged DNA
Acetylation and bromodomians
histone acetylation generates binding sites for bromodomains. The bromodomains then recruit other proteins like nucleosome remodeling complexes
What is methylation associated with
activation or repression (depends on residue); position and modification are important for regulation
methylation of lysine 9 in H3
asso with silent chromatin
methylation of H3 lysine 4
asso with active chromatin
What are chromodomains associated with
bind specific methylated lysines; transcriptional silencing
Describe the histone hypothesis
different modification patterns act like switches to regulate different processes; the combination of different mods can send different signals to the cell
