Shemanko Lecture 4 Flashcards
How does the cell remember what genes to turn back on when polymerase 11 leaves the dna and stops transcribing genes?
Through bookmarks- epigenetic markers and protein partners that leave instruction the genes
Can bookmarks be reprogrammed?
yes through micro-environments and cancer
What is heterochromatin, what is euchromatin?
Chromatin that remains tightly packed after mitosis is called heterochromatin
Euchromatin is chromatin returns to a dispersed state after mitosos
What do chromosomes consist of?
chromatin fibers, histones, and dna and histones are organized into subunits called nucleosomes
What does histone H1 do?
links nucleosomes
What is the structure of nucleosomes?
Dna is wrapped around a core complex, this complex has two of each histone H2A, H2B, H3, H4. Has histone H1 outside of it linking it to other nucleosomes
What is the structure of histones?
Each histone has a flexible amino-terminal tail that sticks out past DNA
What do histones do?
Can modify character of nucleosomes
Histones, regulatory proteins and enzymes help mediate DNA transcription, compaction, replication, recombination, and repair
What is the histone code?
Histone tail modifications; tails of histones can recruit nonhistone proteins which changes the way histones of neighboring nucleosomes interact this includes phosphorylation, acetylation, methylation, or ubiquitenation
What is the histone code hypothesis?
states that the activity of a chromatin region depends on the degree of modification of the histone tails
Can small RNA’s silence chromatin?
yes by recruiting proteins that modify histones
How is DNA and histones methylated?
A methyl group is added to the 5 carbon position of cytosine residues in DNA by DNA methyl transferases
Histones are methylated on arginine anD LYSINE residues by histone methyl transferases.
How are histones acetylated?
by actylation on lysine through HAT (histone acetyl transferases)
How are histones deactylated?
by deacetylation on lysine through HDAC (histone deacetylases)
What opens chromatin?
acetylation
What closes chromatin?
deacetylation or methylation
Histone acetyl transferases lead to what?
open chromatin
Histone deacetylases or histone methyltransferases lead to what?
closed chromatin
What kind of machinery does open chromatin allow room for?
allows for room for transcription machinery to find their binding sites
If H3K9 is methylated what happens?
the chromatin becomes closed after recruiting heterochromatin protein 1.
Is H3K9 is acetylated what happens?
The chromatin becomes open
What is HP1?
heterochromatin protein 1, contains a chromodomain which binds to methylated histones
Any protein that has a chromodomain will do what?
bind to methylated amino acids
How does a cell know which genes were on before the cell cycle occurs and drops polymerase during mitossi?
through epigenetic markers
What is a Barr body?
Is a X chromosome that remains condensed and doesn’t become transcriptionally active
How does a Barr body form?
The XIC gene produces XIST RNA which then coats the X chromosome, triggering histone methylation and therefore chromosome inactivation.
What are proginetor cells?
are more specialized then stem cells but as not specialized as cells that have differentiated
How can the mammary gland microenvironment can reprogram cells of other tissues?
you clear out the epithelial lineage cells in the mammary gland and the microenvironment will change gene expression of the new cell, reopen up genes that were inhibited and cause it to be mammary gland cell?
