Northern Blot of tRNA in Yeast

tRNAs are small RNAs around 70-90 nt. tRNAs are different from many other small RNAs in that they are very abundant, which makes it difficult to study their transcriptional regulation by traditional northern blot. Traditional Northern blot involves incorporation of radioactive nucleotides through polymerization, however, tRNA is too short for polymerization. Traditional Northern blot detects changes in RNA levels, however, tRNA are so abundant that small changes in their levels will escape detection. For these reasons, metabolic labeling by radioactive Uracil has been used instead. However, metabolic labeling can only examine changes in total tRNA, but cannot distinguish different types of tRNAs. The following protocol describes a method to examine individual tRNA gene transcription by northern blot.