Colorectal Cancer: From the Genetic Model to Posttranscriptional Regulation by Noncoding RNAs

Figure 2

Interaction between miRNAs and target mRNAs in animals and miRNA-200 family. (a) miRNAs (green) target mRNAs (blue) in the 3′UTR. This mRNA region can bind one or various miRISC complexes arising from the same or different miRNAs. A perfect complementarity is found in the seed region between nucleotides 2 and 7 from the 5′ end of the miRNA (orange box). A central bulge prevents endonucleolytic cleavage mediated by Ago2 (a major difference with the miRNA-target mRNA interaction in plants). A few nucleotide matches in the miRNA 3′ end (especially between nucleotides 13 and 16; yellow box) are necessary for the best stabilization of the miRNA/mRNA duplex. The presence in the mRNA sequence of an A residue in position 1 and/or an A or U residue in position 9 can increase miRNA efficiency [6]. (b) The miR-200 family of miRNAs consists of two closely related subfamilies that differ in one nucleotide within the seed sequence (boxed). The five miR-200 family members are located on two different genetic loci in chromosomes 1 and 12. (c) Schematic representation of the secondary structure of the pre-miR-141 hairpin. The sequence of the mature miR-141-3p is indicated in red and the miR-141-5p (previously called miR-141) is in blue. Black triangles show Dicer cleavage sites due to its RNase III activity.

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