Cells were collected by centrifugation at 6,000g, resuspended in lysis buffer (50mM Tris/HCl pH 8.0, 500 mM NaCl, 30mMimidazole) and incubated with CPSF6 (500 M final) for 10 minutes. Beads and bound protein were washed with wash buffer (50mM Tris/HCl pH 8.0, 300 mM NaCl, 40mM imidazole). The eluted protein was dialysed into buffer (50mM…