lecture 4 recap Flashcards
whats the histone code
types of modifications on the N terminal tail that tells you what the transcriptional state of the DNA is
chromodomains and PWWP proteins bind to
methylated lysines
how do ATP dependent chromatin remodelers change the structure of chromatin
use energy from ATP hydrolysis
what are the 4 different families of the ATP chromatin remodelers
SWI2/SNF2, ISWI, CHD/Mi2 and Ino80
the can use the energy from ATP hydrolysis to do one or more of these reactions
- slide nucleosomes along DNA
- unwrapping DNA from the nucleosome
- remove nucleosome
- spacing of nucleosomes
5.exchange histones for histone variants
the catalytic subunit of SWI/SNF is
Snf2 or Swi2
Snf2 uses energy from ATP hydrolysis to induce what
torsion which results in disruption of histone-DNA interactins and movement of the nucleosome
they change the position of the DNA around the nucleosome which makes what
potential binding sites accessible
what in the Snf2 help tether it to the acetylated nucleosomes
bromodomains
what can ATP- dependant complexes co operate with
HATs
HDACs commonly function in large multi subunit complexes for example
SIN3 co repressor
how HDACs work:
URS is bound to by
DNA binding domain on Ume6 (repressor protein)
Ume6 binds to HDAC complex and brings it to the chromatin. what subunit in the HDAC deacetylates the lysines?
Rpd3
what are co-repressors
repressors that dont bind to DNA directly
what family of ATP dependent remodellers does NuRD complex belong to
Mi2/CHD family
NuRD cause the chromatin to be more
tight and causes a closed chromatin structure turning transcription off
what the the two types of chromatin
heterochromatin and euchromatin
euchromatin is
gene rich and has the potential to be transcribed
heterochromati is
gene poor, contains repetitive regions and associated with transcriptional silencing
where is hetermochromatin found
at centromeres and telomeres
heterochromatin has specific methylation of what
H3 (Lys9 and Lys27)
assembly of H3Lys9me
in order for a lysine to be methylated it bust be
deacetylated
what removes that acetyl group
HDACs
methylation of Lys9 on histone H3 is mediated by
suvar39
methyl on Lys9 is recognised by
HP1 (heterochromatin protein 1)
HP1 is a
chromodomain proteins
HP1 binding to methylated H3Lys9 is thought to do what
compact nucleosomal arrays by interacting with itself
HP1 also acts as an interation platform for what
further activities that prevent recruitment and activity of RNA pol II
