clear my concept

[af malik]

Hi,
is there any differences between the pathway of siRNA and miRNA gene down regulation.besides the differenec of exo and endogenous production n specificty are there any differences b/w the two?sinec both work through RNAi than what are the possible way of differentiating them.also tell me clearly which molecule act at which level i.e transcriptional or translational?why in animals miRNAs are complementary to the 3 prime UTR where as in plants with coding region?plz answer me n provide me more information because i am interested in gaining knowlwdge about them.
awaiting,
af malik

[Jon Moulton]

Hi Malik,

OK, these are my opinions on these topics. I hope someone picks up the argument.

The only difference between siRNA and miRNA is their origin. If the molecules are endogenous to a creature's wild-type genome, they are miRNA; if they are lab-synthesized or expressed from an exogenous plasmid, they are siRNA.

Regardless of their origin, the molecules may have effects at both the transcription and translation levels.

In animals, as in plants, MRE may be found in the 3'-UTR or in the coding region.

In support of the latter point, see:
[Only registered users see links. ]
Nature. 2008 Sep 17. [Epub ahead of print]
MicroRNAs to Nanog, Oct4 and Sox2 coding regions modulate embryonic stem cell differentiation.
Tay Y, Zhang J, Thomson AM, Lim B, Rigoutsos I.