RNA Isolation and Blot Hybridization

Total RNA was extracted as described［9］.After the RNA was denatured in formaldehyde，it was fractionated by electrophoresis in 6%formaldehyde/1.2%agarose gels［24］and transferred to GeneScreen membranes（New England Nuclear）［25］.The plasmid DNA was labeled with［α-32P］dCTP by nick-translation.The M13 phage DNA was labeled with［α-32 P］dATP by extension of the annealed sequence primer with DNA polymerase ⅠKlenow fragment at 15℃for 1 h，using 50μCi（1 Ci=37 GBq）of［α-32 P］dATP in 20 μl of 10 mmol/L Tris.HCl/1 mmol/L MgCl2/60 mmol/L NaCl/1 mmol/L dithiothreitol/0.2 mmol/L dCTP/0.2 mmol/L dUTP/0.2 mmol/L dGTP，pH 7.9.The oligonucleotide probes were 5-end-labeled by the polynucleotide kinase reaction［26］.Dot blot and electropherogram-replica hybridizations were as described［25］.To quantitate hybridization，autoradiograms were scanned with a GS 300 transmittance-reflectance scanning densitometer（Hoefer，San Francisco）.(https://www.daowen.com)