In molecular biology mir-22 microRNA is a short

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...

molecule.

MicroRNA MicroRNA (miRNA) are small, single-stranded, non-coding RNA molecules containing 21 to 23 nucleotides. Found in plants, animals and some viruses, miRNAs are involved in RNA silencing and post-transcriptional regulation of gene expression. miRN ...

s are an abundant class of molecules, approximately 22

nucleotide Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules wi ...

s in length, which can post-transcriptionally regulate gene expression by binding to the

3' UTR In molecular genetics, the three prime untranslated region (3′-UTR) is the section of messenger RNA (mRNA) that immediately follows the translation termination codon. The 3′-UTR often contains regulatory regions that post-transcriptionally ...

of mRNAs expressed in a cell.

Origins

Mir-22 was originally identified in

HeLa HeLa (; also Hela or hela) is an immortalized cell line used in scientific research. It is the oldest and most commonly used human cell line. The line is derived from cervical cancer cells taken on February 8, 1951, named after Henrietta La ...

cells (an immortal cell line derived from cervical cancer cells), but was later found to be ubiquitously expressed in various tissues. The gene encoding miR-22 is found on the short arm of

chromosome 17 Chromosome 17 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 17 spans more than 83 million base pairs (the building material of DNA) and represents between 2.5 and 3% of the total D ...

, in a minimal loss of heterozygosity region. It is highly conserved across many vertebrate species, including chimp, mouse, rat, dog and horse. This level of conservation suggests functional importance. MiR-22 was previously identified as having a role in erythrocyte maturation.

Role in cancer

The deregulation of many miRNAs has been shown to have a role in

oncogenesis Carcinogenesis, also called oncogenesis or tumorigenesis, is the formation of a cancer, whereby normal cells are transformed into cancer cells. The process is characterized by changes at the cellular, genetic, and epigenetic levels and abnor ...

. Mir-22 was found to be over-expressed in prostate cancer but down-regulated in breast cancer,

cholangiocarcinoma Cholangiocarcinoma, also known as bile duct cancer, is a type of cancer that forms in the bile ducts. Symptoms of cholangiocarcinoma may include abdominal pain, yellowish skin, weight loss, generalized itching, and fever. Light colored stool ...

multiple myeloma Multiple myeloma (MM), also known as plasma cell myeloma and simply myeloma, is a cancer of plasma cells, a type of white blood cell that normally produces antibodies. Often, no symptoms are noticed initially. As it progresses, bone pain, an ...

and

hepatocellular carcinoma Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults and is currently the most common cause of death in people with cirrhosis. HCC is the third leading cause of cancer-related deaths worldwide. It occurs in t ...

. Mir-22 expression was associated with survival in multiple breast cancer datasets.

Targets

Specifically, miR-22 can function as a

tumour suppressor A tumor suppressor gene (TSG), or anti-oncogene, is a gene that regulates a cell during cell division and replication. If the cell grows uncontrollably, it will result in cancer. When a tumor suppressor gene is mutated, it results in a loss or red ...

. One known target is

histone deacetylase Histone deacetylases (, HDAC) are a class of enzymes that remove acetyl groups (O=C-CH3) from an ε-N-acetyl lysine amino acid on a histone, allowing the histones to wrap the DNA more tightly. This is important because DNA is wrapped around his ...

4 (HDAC4), which is known to have a critical role in cancer development. Mir-22 also targets

Myc ''Myc'' is a family of regulator genes and proto-oncogenes that code for transcription factors. The ''Myc'' family consists of three related human genes: ''c-myc'' (MYC), ''l-myc'' (MYCL), and ''n-myc'' (MYCN). ''c-myc'' (also sometimes referre ...

Binding Protein (MYCBP). This prevents transcription of c-Myc target genes by silencing c-MYCBP. However, c-Myc also inhibits expression of miR-22 in a

positive feedback loop Positive feedback (exacerbating feedback, self-reinforcing feedback) is a process that occurs in a feedback loop which exacerbates the effects of a small disturbance. That is, the effects of a perturbation on a system include an increase in the ...

. When this spirals out of control, it can cause uncontrolled cell proliferation.

Possible therapy

Expression of miR-22 can be induced by adding 12-O-Tetradecanoylphorbol-13-acetate (TPA) to HL-60 cells (leukaemia cell line). The enforced expression causes the growth of cancer cells to slow down. This means that miR-22 could be a potential target for cancer therapies.

References

External links

* {{miRNA precursor families MicroRNA