Role of miRNA in liver

Role of miRNA in liver cancer

MicroRNAs (miRNAs), discovered by
Ambros and colleagues in 1993,i
are small noncoding RNAs, 18–24 nucleotides in length, that regulate gene
expression by binding to mRNAs to interfere with the process of translation.ii
Genes that encode miRNAs are transcribed from DNA to a primary transcript
(pri-miRNAs), which is processed into a short precursor (pre-miRNA) and then
exported into the cytoplasm where it is further processed into a mature, single
stranded miRNAiii.
Most miRNAs are transcribed from intergenic regions by RNA
polymerase II. The primary transcripts are precursor molecules (pri-miRNA) that
are processed by two ribonucleases—Drosha in the nucleus and Dicer in the
cytoplasm—into mature miRNAs.

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MiRNAs are endogenous and potentially can regulate every aspect of
cellular activity, including development and proliferation, differentiation,
metabolism, viral infection, epigenetic modulation, apoptotic cell death, and
tumor genesis. Recent studies provide evidence that miRNAs are abundant in the
liver and affect a diverse spectrum of liver functions.iv

classes of miRNAs can play oncogenic as well as tumor-suppressing roles; the
same group of miRNAs can exhibit oncogenic activity in one tissue type but act
as a tumor suppressor in anotherv

miRNAs potently influence
cellular behavior through the regulation of extensive gene expression networksvi

It has been demonstrated that
most tumors are characterized by globally diminished miRNA expressionviii.

MicroRNAs, small noncoding RNAs
that regulate the translation of many genes, are excellent biomarkers for
cancer diagnosis and prognosisix

Chronic infections with either
HBV or HCV increase the relative risk of liver cancer greatly. These chronic
viral infections are present in more than 70% of HCC cases, and iatrogenic
interventions against these viruses significantly reduce the risk of HCC