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An oncomir (also oncomiR) is a microRNA (miRNA) that is associated with cancer. MicroRNAs are short RNA molecules about 22 nucleotides in length. Essentially, miRNAs specifically target certain messenger RNAs (mRNAs) to prevent them from coding for a specific protein. The dysregulation of certain microRNAs (oncomirs) has been associated with specific cancer forming (oncogenic) events. Many different oncomirs have been identified in numerous types of human cancers.〔 Oncomirs are associated with carcinogenesis, malignant transformation, and metastasis. Some oncomir genes are oncogenes, in that overexpression of the gene leads to cancerous growth. Other oncomir genes are tumor suppressors in a normal cell, so that underexpression of the gene leads to cancerous growth.〔〔〔〔 ==General mechanism== Oncomirs cause cancer by down-regulating genes by both translational repression and mRNA destabilization mechanisms.〔 These down-regulated genes may code for proteins that regulate the cell's life cycle. Oncomirs may be at increased or decreased levels within cancerous tissue. In the case of increased oncomir activity, the oncomir is likely suppressing a tumor suppressor gene. In cases of underexpressed oncomirs, regulation is attenuated, allowing the cell to proliferate freely.〔 Viruses have also been found to have miRNA that mimic parts of natural regulatory human miRNA's. One example is the Epstein–Barr virus (EBV) which is associated with various types of cancer.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Oncomir」の詳細全文を読む スポンサード リンク
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