Which strand in an miRNA precursor will serve as the guide strand in the RNA-induced silencing complex (RISC)? Analysis of miRNA sequences has revealed an asymmetry in the stability of the double-stranded RNA precursor. The strand showing lower thermodynamic stability near its 5? end (nucleotides 2 to 6 in the mature guide strand) is normally selected as the guide strand, and the other strand is usually degraded. In the following miRNA precursor, which strand (1 or 2) do you think will be incorporated into the active RISC? Write down 1 or 2 as your answer.

Question

Quizplus · Accepted Answer

Note the presence of mismatches and even a bulge along the duplex. Strand 1 contains mostly A-U base pairs, as well as a mismatch, near its 5? end (left). Strand 2 contains mostly C-G pairs near its 5? end (right).

Which Strand in an MiRNA Precursor Will Serve as the Guide