Human Argonaute Immunoaffinity Purification-associated RNA

Immunoaffinity Purifications of Human Argonaute Twelve hours after transfections with mock or with miR-124, we washed each 15-cm plate once with phosphate-buffered saline (usually two plates were used per IP), then added 1 ml of 4 C lysis buffer (150 mM KCl, 25 mM Tris-HCl [pH 7.4], 5 mM Na-EDTA [pH 8.0], 0.5% Nonidet P-40, 0.5 mM DTT, 10 ul protease inhibitor cocktail [Pierce Cat# 78437], 100 U/ml SUPERaseIn [Ambion Cat# AM2694]). Following a 30-min incubation at 4 C, we scraped the plates, combined the lysates, and then spun them at 4 C for 30 min at 14,000 RPM in a microcentrifuge. We collected the supernatant and filtered it through a 0.45-um syringe filter. We froze an aliquot of lysate in liquid nitrogen for reference RNA isolation. We then added 0.22 mg/ml heparin to the lysate. We mixed the lysate with 2.5 mg of Dynal m-280 streptavidin beads (250 ul from original storage solution) coupled to biotinylated 4F9 ago antibody (~12.5 ug), which we equilibrated immediately prior to use by washing twice with 1 ml of lysis buffer. We incubated the beads with the lysate for 2 h at 4 C and then washed the beads twice with 1.25 ml of ice-cold lysis buffer for 5-min each. Five percent of the beads were frozen for SDS PAGE analysis after the second wash. RNA was extracted directly from the remaining beads using lysis buffer from Invitrogen's Micro-to-Midi kit (Invitrogen Cat# 12183-018). We purified RNA from the lysate and RNA extracted from the beads with the Micro-to-Midi kit as per vender's instructions, except that the percentage isopropanol used for binding to the column was 70%, instead of 33%, to promote the binding of small RNAs. RNA was amplified with ambion kit 1755. RNA from total cell lysate was labeled with cy3 and IPd RNA was labeled with cy5 An all pairs experiment design type is where all labeled extracts are compared to every other labeled extract.