lecture 13 Flashcards
5 ways to treat errors in DNA
- methylation drugs
- homologous recombination
- gene therapy
- artificial repressors or activators
- CRISPR/Cas9
how to stop methylation
methylation stops transcriptions
usually happens to cytosine
add 5-azacytidine.
this can not get methylated. will prevent methylation.
Issues: could be a treatment for b-thalassemia p with issues with Bglobin locus -would effect all cells not just cytosine
-would be lethal
homologous recombination
correct sequence would replace incorrect sequence
issues: might not work
might bind to wrong cells or not bind to the correct cells
inefficient
gene therapy
how does it work
issues
replacement therapy
retovirus would have new gene, gets put back into person
issues: can have immune response to retoviral
- can get too high or too low expression
- can lose retovirus
- retovirus lives in nucleus, can insert into the genome and lead to other errors
- can only treat certain diseases
artificial repressor or activators
examples
issues
zinc fingers, Talen
issues: not really efficient, expensive
CRISPR/Cas9
RNA directed guide
- very specific
- very efficient
Cas9 protein will make break in gene
- small amount of off target sites
- multiple targets at once
Cas9 can be linked with repressors or activators
three ways to target things
Zn fingers
- can bind at random stops
- not efficient
TALENS
- can bind at random stops
- not efficient
CRISPR
RNA directed guide
-very specific
-very efficient
medical treatment at the level of RNA
RNAi
ribozymes
antisense technology
target and destroy specific RNA
inhibits RNA by targeting it for degradation
-inhibits at level of DNA by repressing transcription
- specificity not that great
- works in lab not in person yet
medical treatment at the level of proteins
- inhibition of protein modifications
- specific protein inhibitors
- molecular mimetics- predict sequence and shape
example : philadelphia chromosome
explain treatment for philadephia chromosome
translocation of 9 and 22 chromosomes which create chimera protein- BCR-ABL
kinase that regulates cell growth- this chimera will deregulate the protein to always on which creates (CML) leukemia
-imatinib (Gleevec, Novartis)
will inhibit BCR-ABL
competitive inhibitor
40% cured
issues:
mutations in ATP binding pocket, changes formation and imatinib can no longer bind
-amplification of BCR-ABL
*** your patient’s beta-globin gene is silent due to DNA methylation. What compound could be given to demethylate the DNA and activate the gene
5-azacytidine
replace the cytosine with another base that can not be methylated
***RNAi can inhibit expression in 2 ways. What are they?
bind to mRNA and degrade the mRNA
inhibit at the level of DNA by repressing transcription
medical treatment at the level of RNA with RNAi
inhibits RNA by targeting it for degradation
-inhibits at level of DNA by repressing transcription
