Does the isolated RNA fraction contain a mixed population of mature and precursor miRNA ?
The isolated small RNA fraction may contain precursor miRNAs; circumstantial evidence, however, suggests that this may not be the case. The following observations support this: A. Existing papers agree that miRNA precursors turn over very quickly. Even if they were labeled, the signal contributed would be negligible. B. The reverse sequences of several miRNAs printed on the array do not light up, as is expected if only the mature miRNA is labeled. C. We have designed primers for qRT-PCR in the stem loop region of the precursor miRNA and seen Cts at least 5-6 behind that of the mature miRNA.
