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| Question | Answer |
| advantages of triple helix....but | 1. effective when it works 2. low levels of oligonucleotides req 3. viruses can code encode changes into cells for continual expression 4. not yet acheived |
| why don't triplexes work well? | DNA supercoiled with histones attached. most of experiments done in microbes with less complex DNA. |
| why is triplex better than anti sense? | 1. fewer molecules needed 2. low dose long acting therapy 3. turns off genes |
| sequence selective recognition and cleavage of double stranded DNA | same as anti sense strategy |
| ribozymes | 1. naturally occuring RNA sequences 2. cleave at GUC 3. must target ribozyme to correct mRNA 4. |
| take home message on anti sense and other silencing techniques | Anti-sense is simple and has had some success. Triple helix and ribozyme technology is just to difficult to use. |
| RNA interference | long dsRNA is cleaved into smaller segments of 21 to 23 nucleotides, called small interfering RNA (siRNA), by type III RNases. These act as guides, binding to the corresponding segments of an mRNA. Following binding to the mRNA, the siRNA guide recruits cellular enzymes that cleave and destroy the mRNA. |
| siRNA (snall interfering RNA) | The small size enables supress gene expression without undesirable cellular responses. SiRNA-based drugs can distinguish between a normal and a mutated sequence that differ by only one nucleotide. |
| the ideal oligonucleotide | 1. stable DNA/RNA complex 2. specific targeting 3. long half life/resistant to nuclease 4. pass easily through cell membranes 5. must not accumulate in organs/organelles 6. 18-20 bp long |
| Ways to deliver antisense molecules | 1. delivered within liposomes or attached to factors to allow receptor mediated binding 2. Viruses 3. injection. 4. DNA cream |
| Uses of anti sense molecules | 1. treat infectious disease 2. treat cancer 3. dominant disease genes (in theory) 4. to study effects of turning genes off |
| triple helix technology= triplex | a molecule that can bind to DNA in the chromosome to turn off the gene |
| anti sense molecules | short ss piences of DNA that block translation of mRNA into functional protein |
| modifications to make an anti sense molecule | cannot effect binding capacity! 1. replacemtn of phosphate oxygens. 2. nucleosides 3. addition of FeEDTA 4. acridine dye |
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