Polyclonal antibody for Rho (gift from Jeff Roberts)
Treatment protocol
Cells were grown with vigorous shaking at 37 °C to mid-log (light scattering at 600 nm equivalent to 0.4 OD). Sodium phosphate (1/100 vol. of 1M, pH 7.6; 10 mM final) was added to the mid-log cultures followed by formaldehyde to 1% final, and shaking was continued for 5 min. Cold 2.5 M glycine was added to 100mM and the mixture was incubated at 4 °C with agitation for 30 minutes to stop the crosslinking. Cells were spun at 5000 x g, and washed repeatedly with phosphate buffered saline before being frozen at -80 °C.
Growth protocol
Strain MG1655 or isogenic strain MG1655 HA3::nusG cells were grown in MOPS minimal medium supplemented with 0.2% glucose (www.genome.wisc.edu/resources/protocols/mopsminimal.htm).
Extracted molecule
genomic DNA
Extraction protocol
Cell pellets (from initial 50 ml of culture) were thawed and resuspended in 250ul of IP buffer (100 mM Tris pH 8, 300 mM NaCl, 2% TritonX-100) and sonicated using a microtip sonicator set at 10% output for 20 second intervals with periods of cooling in between. Cells were then treated for one hour at 4 °C with RNase A (2 ng/ml) micrococcal nuclease (50 units), 20 μM CaCl2,1.2 mM KCl, 0.3 mM NaCl, 6 mM sucrose, and 10 μM DTT. After treatment, a distribution of DNA fragments ranging from 200-600 bp was detected by agarose-gel electrophoretic separation of a small sample that was de-crosslinked by incubation at 65 °C for >4 hr. EDTA was added to 10 mM to stop the micrococcal nuclease and the samples were spun down to remove cell debris. The lysate was then incubated with a 50/50 slurry of Sepharose protein A beads and protein G beads in IP buffer for 2-3 hours at 4 °C. The beads were removed by centrifugation and antibody was added to the pre-cleared lysate for an overnight incubation. The next day, 30 μl of a 50/50 slurry of Sepharose protein A and G beads in IP buffer was added to the lysate to capture antibody-protein-DNA complex for one hour at 4 °C. Beads were then washed once with 1 ml of 250 mM LiCl wash buffer (100 mM Tris pH 8, 250 mM LiCl, 2% TritonX-100), twice with 600 mM NaCl wash buffer (100 mM Tris pH 8, 600 mM NaCl, 2%SDS), twice with 300 mM NaCl wash buffer (100 mM Tris pH 8, 300 mM NaCl, 2%SDS), and twice with TE. Elution buffer (50 mM Tris pH 8, 10 mM EDTA, 1% SDS) was added after the final wash step, and beads were incubated at 65 °C for 30 minutes toremove the crosslinked protein-DNA complexes from the beads. After centrifugation to remove the beads, the samples were incubated overnight at 65 °C to reverse the protein-DNA formaldehyde crosslinks. DNA was purified using Qiagen’s PCR Purification kit and eluted to a final volume of 50ul with EB.
Cells were grown with vigorous shaking at 37 °C to mid-log (light scattering at 600 nm equivalent to 0.4 OD). Sodium phosphate (1/100 vol. of 1M, pH 7.6; 10 mM final) was added to the mid-log cultures followed by formaldehyde to 1% final, and shaking was continued for 5 min. Cold 2.5 M glycine was added to 100mM and the mixture was incubated at 4 °C with agitation for 30 minutes to stop the crosslinking. Cells were spun at 5000 x g, and washed repeatedly with phosphate buffered saline before being frozen at -80 °C.
Growth protocol
Strain MG1655 or isogenic strain MG1655 HA3::nusG cells were grown in MOPS minimal medium supplemented with 0.2% glucose (www.genome.wisc.edu/resources/protocols/mopsminimal.htm).
Extracted molecule
genomic DNA
Extraction protocol
Cell pellets (from initial 50 ml of culture) were thawed and resuspended in 250ul of IP buffer (100 mM Tris pH 8, 300 mM NaCl, 2% TritonX-100) and sonicated using a microtip sonicator set at 10% output for 20 second intervals with periods of cooling in between. Cells were then treated for one hour at 4 °C with RNase A (2 ng/ml) micrococcal nuclease (50 units), 20 μM CaCl2,1.2 mM KCl, 0.3 mM NaCl, 6 mM sucrose, and 10 μM DTT. After treatment, a distribution of DNA fragments ranging from 200-600 bp was detected by agarose-gel electrophoretic separation of a small sample that was de-crosslinked by incubation at 65 °C for >4 hr. EDTA was added to 10 mM to stop the micrococcal nuclease and the samples were spun down to remove cell debris. The lysate was then incubated with a 50/50 slurry of Sepharose protein A beads and protein G beads in IP buffer for 2-3 hours at 4 °C. The beads were removed by centrifugation and antibody was added to the pre-cleared lysate for an overnight incubation. The next day, 30 μl of a 50/50 slurry of Sepharose protein A and G beads in IP buffer was added to the lysate to capture antibody-protein-DNA complex for one hour at 4 °C. Beads were then washed once with 1 ml of 250 mM LiCl wash buffer (100 mM Tris pH 8, 250 mM LiCl, 2% TritonX-100), twice with 600 mM NaCl wash buffer (100 mM Tris pH 8, 600 mM NaCl, 2%SDS), twice with 300 mM NaCl wash buffer (100 mM Tris pH 8, 300 mM NaCl, 2%SDS), and twice with TE. Elution buffer (50 mM Tris pH 8, 10 mM EDTA, 1% SDS) was added after the final wash step, and beads were incubated at 65 °C for 30 minutes toremove the crosslinked protein-DNA complexes from the beads. After centrifugation to remove the beads, the samples were incubated overnight at 65 °C to reverse the protein-DNA formaldehyde crosslinks. DNA was purified using Qiagen’s PCR Purification kit and eluted to a final volume of 50ul with EB.
