Figure 4
From: MicroRNA manipulation in colorectal cancer cells: from laboratory to clinical application
Figure shows the proposed mechanism of biogenesis and function of tumour suppressor miRNAs. Promotor hypermethylation/deactylation, homogygous/hetrotogygous deletion, mutation or pleomorphism in miRNA transcription gene results in under production or complete loss of pri-miRNAs. Defects in miRNA processing machinery i.e. ineffective processing by Drosha/Dicer or defective pairing with RISC can result into inefficient levels of mature miRNAs in the cytoplasm. Low levels of tumour suppressor miRNAs result in over expression of oncogenic mRNAs (Ras, Bcl2, Mcl1).