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.
