Lecture 14 Histone Code MCB
what domain do unmodified proteins recruit?
SANT domain
the inactive form of chromatin is...
heterochromatin
heterochromatin
highly compressed the form when transcription is not occuring
a core composed of eight ______ proteins interacts with DNA through hyrdogen bonding and ionic bonds.
histone
what is unique about H2A and H2B in terms of modifications?
it has a C terminal that can be modified
when one gene is deactivated, what affect does it have on all the rest?
it increases the number of inactive genes
on what residues does methylation occur?
lys and arg
what is the effect of HP1?
maintains the condensed chromosome and packs it tighter during duplication
epigenetic regulation accounts for cell __________ and different cell ____________.
memory states
what are the types of epigenetic modifications
methylation acetylation phosphorylation ubiquitination
what is the position effect on gene expression?
moving a gene from euchromatin to heterochromatin or vice versa will affect the expression of the different genes
A ___________ is a DNA protein complex.
nucleosome
if DNA structure is described as "beads on a string" a "bead" is a ________.
nucleosome
The more darkly staining form of chromatin is.....
heterchromatin
what is a barrier DNA sequence?
1. a sequence that attracts a physical barrier protein that blocks the reader writer complex and stops the spread of a certain sequence 2. the protein is an enzyme that breaks down the writer complex
how many DNA molecules are in a lampbrush chromo?
4
How does Epigenetic change differ from a mutation?
A mutation alters the nucleotide sequence in DNA. An epigenetic change doesn't alter the DNA sequence but can be inherited by daughter cells.
what is the major state of genes found in prokaryotes?
Euchromatin because the genes are constantly having to replicate
if DNA is described as "beads on a string" the "string" is the....
DNA molecule
what is the major state of most genes?
Euchromatin
what are the two states of DNA?
Euchromatin and Heterochromatin
examples of histone variants
H2A-X: recruits repair enzymes CENP-A : centromere function; allows attachment of the mitotic spindle to the kinetocore
what is the major form of the Y chromosome?
Heterochromatin (the small leg is euchromatin)
Acetylation is catalyzed by _________ and reversed by _______
Histone Acetyl Transferase Histone DeAcetylase
Methylation is catalyzed by _______ and reversed by_________
Histone Methyl Transferase Histone Demethylase
on what residues does acetylation occur?
Lys
what domains does methylation recruit?
PHD Chromodomain TUDOR
ubiquitination
activation a COO- group to react with amino groups forming what looks like a peptide bond but is really an isopeptide bond
What domain does acetylation recruit?
bromodomain
what is an example of the position effect?
calico cat red and while splotchy fly eyes
ubiquitination is usually used as a target for ___________ but can also act as a new ________ site.
degredation binding
the less condensed form of chromatin is...
euchromatin
euchromatin
expanded form of chromatin form chromatin takes most often during transcription
Lampbrush chromosomes
fully extended and duplicated chromosomes found in the oocyte of animals except mammals; genes that are to be expressed are in a large loop
what happens when there is a phosporylation at the 10th Ser and acetylation at the 14th Lys
gene expression
what happens when there is a methylation at the 9th Lys?
gene silencing
histone variants
proteins that can replace one of the four types of histones and alter nucleosome function
what are the steps to expressing a gene in a lampbrush chromosome?
recruit histone remodeling protein to write the code recruit chromatin remodelers RNA polymerase loop becomes extended
epigenetic regulation
the expression of genes based on the different modifications (active or inactive) is passed on to the daughter cells but there is no change in the DNA sequence
what is the histone code
the specific pattern of modifications
what is the most important part of the histones?
the tails!!
what happens when there is a methylation at the 27th Lys
x-chromosome inactivation/silencing of the HOX genes