RPA of mNC expression in MPRO cells. RNA was isolated from uninduced and ATRA-induced cells at the indicated time points and subjected to RPA using riboprobes for mNC and β-actin. The mNC riboprobe is approximately 500 nt and protects a fragment of 424 nt. The β-actin probe is 330 nt, and the protected fragment is 250 nt. Lane 1, EPRO polyA RNA (500 ng); lane 2, uninduced MPRO; lane 3, MPRO induced with ATRA for 24 hours, lane 4, 48 hours, and lane 5, 72 hours; lane 6, yeast RNA digested with RNase; lane 7, yeast RNA alone, indicating size of undigested riboprobes.