Exam 4 Histones and Nucleosomes and nucleosome assembly
it takes 165 bp to make ____ turns around an octamer
1.67
the core DNA is the length of ______ bp that is found on the core particles produced by prolonged digestion with _________ nuclease
146 micrococcal
what does a nucleosome contain
200 bp of DNA and two copies of each core histone
What would the average size of the fragments of chromatin be if you added just enough nuclease to hit once per nucleosome
200bp
what is the packing raio of the 10 mm fiber
6
_____ acts as a chaperone in both replication dependent and independent nucleosome assembly, feeds the H3/H4 tetramer to CAF1
ASF1
acts as a chaperone in replication dependent nucleosome assembly only
CAF-1
mediate assembly of new H3/H4 nucleosomes on the leading strand duplex
Caf-1 and ASF1
the tetramer binds _______ before it binds ______
DNA H2A/H2B
acts to displace octamers during transcription by releasing H2A/H2B dimers
FACT
binds mostly to linker DNA between nucleosomes has a helix turn helix that binds to any DNA
H1
_____ histones are species specific while ____ is tissue and species specific
H2A H2B H1
which two proteins cap the ends of the core nucleosome
H2A and H2B
what parts of the nucleosome is conserved
H2A and H2B and H3 H4
are two of the most highly conserved proteins in evolution
H3 and H4
is an acetyltransferase that is ascociated with gene activation
HAT
is a deacetylase that is associated with gene expression
HDAC
what protein does replication independent nucleosome assembly use in place of CAF1
HIRA
slowly replaces H3 in non- differentiating cells, and after transcription. used after repair
Histone 3.3
protein that binds the H3/H4 tetramer
N1
which chaperone assembles H2A and H2B
NP nucleoplasmin
caf-1 has affinity for _______
PCNA (clamp)
insulator region found on either side of the 87 heat shock protein
SCS and SCS'
the positive charge of lysine is neutralized by _______ while methylated lysine and arginine retain their positive charges
acetylation
what are the most common types of histone modification
acetylation (HATs and HDACs methylation phosphorylation
nucleoplasmin and the N1 proteins are both ______ and mimic _______
acidic, DNA
FACT remains __________- to the H2A/H2B dimers after transcription to facilitate next round of transcription.
attached
Nucleosomal DNA is divided into the ____ DNA and _____ DNA
core linker
activates a promoter in its vicinity but can be blocked from doing so by an insulator located between them collection of transcriptional activator binding sites
enhancer
is the pattern of modifications present on the tails of histones H3 and H4 that determines the activation state of genes.
histone code
small basic proteins (11 to 15 kDa) that form the interior core of nucleosome.
histones
when are nucleosomes formed?
immediately after replication
an active ________ is a barrier to heterochromatin
insulator
define transcriptionally independent domains
insulators
RNA polymerase and HMGs are considered _______
nonhistone proteins
a) Harder to isolate/purify b) More variable; larger number of proteins c) Smaller portion of the mass than histones d) High mobility group proteins (HMGs) are an example. e) Responsible for higher orders of chromatin structure & control of gene expression
nonhistone proteins
histone octamers are ___ conserved during replication
not
what are the two main classes of nucleosome accessory proteins?
nucleoplasmin and the N1 protein
The fundamental unit of all eukaryotic chromatin. Contains ~200 bp of DNA and 4 histone proteins each in 2 copies. ~50% of mass is histone protein.
nucleosome
light digestion hits between every two __________
nucleosome
nucleosome assembly that occurs during transcription and in cells not undergoing replication
replication independent
where do histone code modifications occur
tails
where are the tails located on the histones and what are they used for
the N terminus of all the histones specific epigenetic markings