MiR-122

mir-122 microRNA precursor
Predicted secondary structure and sequence conservation of mir-122
Identifiers
Symbol	mir-122
Rfam	RF00684
miRBase	MI0000442
miRBase family	MIPF0000095
Other data
RNA type	Gene; miRNA
Domain(s)	Eukaryota
GO	0035195 0035068
SO	0001244

miR-122 is a miRNA that is conserved among vertebrate species. miR-122 is not present in invertebrates, and no close paralogs of miR-122 have been detected. miR-122 is highly expressed in the liver, where it has been implicated as a regulator of fatty-acid metabolism in mouse studies. Reduced miR-122 levels are associated with . miR-122 also plays an important positive role in the regulation of hepatitis C virus replication.

miR-122 was originally identified by cloning of tissue-specific microRNAs in mouse, where its expression is restricted to the liver. The liver-specific expression of miR-122 is conserved in zebrafish. miR-122 expression increases during embryogenesis until it constitutes 72% of total miRNA in adult human liver, making it one of the most highly expressed miRNAs in any tissue. In humans, miR-122 is encoded at a single genomic locus in chromosome 18. The primary miR-122 transcript (pri-miR-122) is a long non-coding RNA. Transcription is regulated by HNF4α. The miR-122 hairpin precursor consensus shown here is predicted based on base pairing and cross-species conservation. The mature sequence is excised from the 5' arm of the hairpin.

There is evidence that miR-122 is regulated by Rev-ErbA alpha which is involved in circadian gene expression, suggesting that miR-122 is a circadian metabolic regulator. miR-122 regulates the expression of several mRNA molecules that are important in the circadian cycle, such as PPARβ/δ. Mature miR-122 is subject to modification by the poly(A) polymerase GLD-2, which adds a single adenosine to the miRNA 3' end. This results in an increase in miR-122 stability.