As we know pri-miRNA contains two strands, which one of them is (exactly or partly ) complementary to target mRNA (antisens - miRNA) and the other one is (exactly or partly ) same as a sense strand or miRNA*. This is the question: how does the RISC complex recognize one of them as a miRNA and why the other strand (miRNA*) is not attaching to the RISC?
If the RISC chose the wrong strand it won't work and the post transcription regulation will fail. So, there should be a mechanism to choose the correct strand, what's the strategy?
Strand selection might be dependent on the thermodynamic stability of the two ends of the duplex. The strand with relatively unstable base pairs at the 5′end typically survives (for example, a GU pair compared with a GC pair) (Kim et al. 2009.Nat.Rev.Mol.Cell Biol.). But this is not stringent. Sometimes both mir-126 and mir-126* can be loaded on RISC and suppress CXCL12 in breast cancer metastasis (Zhang et al. 2013.Nat. Cell Biol.)
Good question Aref
Many theories around... but the one that I like the most is the most simple and the one that makes more sense. In fact there are some authors claiming that cell will select one of the miRNA-generating strands by the presence of the cognate target. If the target is there, the cell will select the strand that recognizes the target and the other one will be degraded. What do you think ?. Nice, isn't it
Best. Paco
Strand selection might be dependent on the thermodynamic stability of the two ends of the duplex. The strand with relatively unstable base pairs at the 5′end typically survives (for example, a GU pair compared with a GC pair) (Kim et al. 2009.Nat.Rev.Mol.Cell Biol.). But this is not stringent. Sometimes both mir-126 and mir-126* can be loaded on RISC and suppress CXCL12 in breast cancer metastasis (Zhang et al. 2013.Nat. Cell Biol.)
dear Ruhul Amin
would you pleas guide me through a good article around the topic? thanks....
thank you Francisco Enguita... yes...it's nice ... whole the biology and specially genetics is nice and interesting ...
may I asked a question, pleas?
do you mean it's depend on the chance?
I mean both of them can join to the RISC but which one recognize the target is the selection tool?
Exactly Aref... So, depending on the relative abundance of the target, the cell will select the miRNA strand that will regulate this target. You can have also considerations of physical chemistry to defend the stability of the hybrid miRNA-target vs the miRNA alone, but I think that globally makes sense. I like the idea of "easy-thinking" to explain cell function.
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