miRBase precursor stem loop structure predicted or experimentally validated?

Question

[rajeshkumar_vinod]

are precursor secondary structures(stem loop) in miRBase experimentally validated?

if not what tool do they use to predict that structure?

[biolab]

Some miRNAs are well validated, take let-7 for example (http://mirbase.org/cgi-bin/mirna_entry.pl?acc=MI0000001), you can find experimental evidences on Evidence row. However, not all miRNAs on miRBase were well experimentally verified, most of which, from my observation, were derived from small RNA seq. miR has higher RPKM abundance than miR* (now it changed to use terms -5p, -3p). Hope this helps.