Epigenetics Flashcards
Epigentics
Alteration of gene expression WITHOUT changes in the gene’s nucleotide sequence
Global hypomethylation
- Hypomethylated DNA is available for transcription
- Good for oncogenes
- Hypomethylated DNA is genetically unstable
Selective promoter
- localized hypermethylation
- Using CH3 to inactivate tumor suppressors
Tumor suppressors inactivated by selective promotors
BRCA1 in breast and VHL in renal cell carcinoma
Primarily acetylation
- to make histones more or less positively charged
- DNA (-) bound more or less tightly to histone proteins in nucleus
More positive charge: Negatively charged DNA binds tight, so less transcription
Can shut off tumor supressors
Less positive charge: DNA binds less tightly–more transcription
Can turn on oncogenes
Chromatid-modifying enzymes
Similar to histones–changes “packing” of DNA within the cell to make it more or less available for transcription
miRNA: Noncoding single strand RNA approximately 22 nucleotides
Targets the 3’ UTR of messenger RNAs
When bound to 3’ UTR, makes the messenger RNA _____ ______ and more likely to be ______.
Less stable and more likely to be degraded
Note: This reduces the amount of that messenger RNA, and thus the expression of the gene it encodes
Increase microRNA to decrease ___________.
Expression of tumor suppressors
Decrease micro RNA to increase __________.
Expression of Onco genes
miRNAs silence by creating …..
double stranded RNA
Ancient anti-viral “immune system” within an eukarytoic cell is triggered by the presence of _______, since it may represent a virus.
double stranded RNA (created by microRNA)
RISC (RNA induced silencing complex) including the protein DICER recognizes dsRNA, such as a micro RNA bound to mRNA
RISC degrades the dsRNA, and keeps a small piece (about the size of a miRNA) which it uses to screen other RNAs in the cell. If the piece it binds matches, RISC kills that too.
What is used to create siRNA?
DICER
siRNA
- is short interfering RNA
- which is RNA about 20-22 nt
- complimentary to the coding portions of mRNAs (unlike the 3’ UTR targeted by endogenously made miRNA)
miRNA is made…
endogenously
How is siRNA made?
- siRNA is produced either by adding siRNA to the cell (experimentally or therapeutically)
- or created when a much longer RNA is complimentary to a mRNA, creating dsRNA.
- DICER then chops up the long dsRNA to create siRNA (process not fully understood) which it uses to silence complimentary mRNA
What chops up the long dsRNA to create siRNA to use to silence complimentary mRNA
DICER
siRNA is being studied to treat cancer…TRUE OR FALSE?
TRUE
