Validation of small RNA accumulation at CTU50. (A) Small RNA distribution. (B) Low-molecular weight RNAs isolated from various cell lines as indicated above each lane were separated by denaturing gel electrophoresis and analyzed by Northern hybridization with two oligonucleotides representing the most abundant reads. Loading control (load), hybridization to 5S rRNA. See additional file 5 for sequences of the hybridization probes.