Block 2 Flashcards
Turning off expression without changing the code..
Epigenetics
Transcription factors are…
Proteins
Epigenetics
A change in the expression of a gene that changes the phenotype without permanently changing the gene itself. Typically involving changes in chromatin structure.
Euchromatin
loose and can actively transcribe
Heterochromatin
Dense packing of DNA, which makes it less accessible
HAT
histone acetyl transferase –> euchromatin
HDAC
histone deacetylase –> heterochromatin
Cis
Elements of DNA that are inactive without a protein bound. Do not have a fixed location, could be a promotor, enhancer, silencer.
Trans
Proteins that bind to cis-acting sequences. They can activate or repress transcription.
HIF-1a is hydroxylated the degraded by proteosomes when?
High oxygen
HIF-1a stabilized, moves to the nucleus and dimerizes with HIF-1B to activate multiple genes that enhance oxygen delivery to tissues and/ or energy supply via glycolysis when?
Low/ no oxygen
In a human cell and under normal atmospheric conditions, certain amino acids found on the HIF-1a peptide will hydroxylate by what enzyme?
Prolylhydroxylase complex
What is the nucleosome core composed of?
2 molecules of H2A, H2B, H3 and H4
Increases Gene Expression
enhancer
Why is DNA methylated in eukaryotes?
To form heterochromatin and keep genes in the region turned off
What neutralizes the charges on histones and loosens up interactions between histones and DNA?
Acetylation
Deacetylation
HDACs
Acetylation
HATS (loosen histones)
Methylation
add a CH3
Dnmt3
responsible for de novo methylation of DNA
Dnmt1
maintenance
MeCP2
binding protein
mSin3A
helps HDACs
GR forms a dimer with?
Cortisol
What influences differential splicing?
Proteins expressed differently in cells
What happens to mRNA molecules with long poly-A tails?
Translated in the cytoplasm
What happens with an mRNA molecule has only part of its poly-A tail?
Remains untranslated
Unfertilized oocyte
5’ guanosine is not methylated and cannot be translated
Fertilized Oocyte
5’ guanosine has 7- methyl and can be translated
Oogenesis-
Oocyte growth:
Oocyte cleavage:
Oocyte growth: long poly-A tails and immediately translated
Oocyte cleavage: poly-As clipped off, translation blocked
After Oocyte fertilization translation stops because?
Poly-A tails are removed
After Oocyte fertilization translation begins because?
Long poly-A tails
What does CPEB do?
Recruits maskin
What does Progesterone do to CPEB?
Activates protein kinase that phosphorylates CPEB and maskin is released and translation can proceed
What binds to initiate translation for interfering proteins?
PABP
What is the function of Puf proteins when bound?
Inhibit translation (inhibit ribosome binding and inhibit a long poly-a tail)
When GF is inactive it is bound to?
heat shock proteins
Unfertilized eggs are hidden by ? and are not translated
RNPs
At fertilization what releases the masking proteins to allow for translation?
ionic changes
What is the function of IRES in eukaryotic mRNA?
It allows the translation of uncapped mRNA
What does Bicoid protein bind to that inhibits translation?
Caudal mRNA
Why is caudal mRNA less inhibited at the posterior end of the fruitfully?
Because there is less Bicoid protein
Where is the most abundant spot of Bicoid protein in a fruitfully?
Anterior
Function of Bicoid protein?
Inhibit translation
Low iron
Transferrin receptor on
Ferritin expression off
High iron
Transferrin receptor off
Ferritin expression on
What is differential splicing?
RNA processing of PRIMARY transcripts which lead to the production of mRNAs which encode for DIFFERENT proteins.
Exons are spliced in certain ways that yield ALTERNATE mRNA transcripts.
