P-GSE45105-1 - P-GSE45105-1
Flies are grown in population cages. After the larvae mature into flies in the inoculated tubs, the flies are transferred to the population cages. The adult flies are raised over a 22-day cycle, with cycles overlapping so that when one adult population has become less productive, another is ready to take its place. Growth conditions and collection protocol to harvest third instar larvae from bottles. Drosophila tissues were homogenized, and treated with formaldehyde. Nuclei were lysed with SDS and sonication in the presence of protease inhibitors. The resulting chromatin was treated with non-ionic detergents at physiological concentrations of monovalent cations. 1. Add 30ml of PAS (50% suspension in RIPA (-PMSF)) to 500ml of crosslinked chromatin. Incubate 1h at +40C. 2. Spin suspensions for 2min at top speed +40C. Transfer supernatants to new tubes. Add 5ml of 100mM PMSF solution in isopropanol to each 500ml aliquot of precleared chromatin. 3. Add appropriate amount of antibody to each reaction. Do not forget to set up no Ab control. Incubate for 15 hours at +40C on rotating weel. 4. Add 40ml of PAS (50% suspension in RIPA (-PMSF)), incubate 3h at +40C on rotating weel. 5. Wash the beads 5 times 10min each with 1ml of RIPA, then one time with 1ml of LiCl ChIP buffer and finally twice with 1ml of TE. To pellet the beads between washes spin samples for 20sec +40C at top speed. Do all the washes at +40C. 6. Resuspend the beads in 100ml TE add 1ml (final 50mg/ml) of RNAse A (10mg/ml) incubate 30min at +370C. 7. Add 7.5ml (final 0.5%) of 10% SDS and 3.8ml (final 0.5mg/ml) of Proteinase K (20mg/ml). Incubate overnight at +370C. 8. Transfer samples at +650C, incubate 6h. 9. Add 4.5ml of 5M NaCl (140mM final). Extract samples with 150ml of phenol-chloroform by vortexing for 30 sec, centrifuge for 10 min at RT, take 120ml of aqueous phase, back-extract organic phase with 150ml of TEN 140 (10mM Tris-HCl pH8.0; 1mM EDTA; 140mM NaCl). Take 150ml of aqueous phase. Combine aqueous phases (you will get 120ml + 150ml=270ml of solution). 10. Extract samples with 300ml of chloroform by vortexing for 30 sec, centrifuge for 5 min at RT. Transfer the upper aqueous phase into the new tube. Add 30ml of 3M NaAc pH 5.0 and 2ml of glycogen (5mg/ml) to aqueous phase. Precipitate DNA with 900ml of EtOH at -700C for 1h. 11. Spin for 10min, top speed at +40C. Wash the pellet in 300ml of 70%EtOH 12. Spin for 10min, top speed at +40C. If you plan to do qPCR analysis only dissolve the pellet in 150ml of pure H2O. If you plan to do both qPCR and microarray hybridization then first dilute DNA pellets in 12ml of pure H2O transfer 4ml of DNA solution to a new eppendorf tube and add 46ml of pure H2O. Use the latter for qPCR and the former for subsequent amplification and labeling. Store DNA solutions at -200C. 13. Prepare dilutions of DNA isolated from the original crosslinked chromatin (also called ?Input DNA? or simply ?Input?) following the chart below. Use the stock with concentration of 0.5% of input DNA per ml of solution (see: ?Isolation of ChIP Input DNA? protocol).