Let-7 microRNA family
| let-7 microRNA precursor | |
|---|---|
Predicted secondary structure and sequence conservation of let-7 | |
| Identifiers | |
| Symbol | let-7 |
| Rfam | RF00027 |
| miRBase | MI0000001 |
| miRBase family | MIPF0000002 |
| Other data | |
| RNA type | Gene; miRNA |
| Domain(s) | Eukaryota |
| GO | GO:0035195 GO:0035068 |
| SO | SO:0001244 |
| PDB structures | PDBe |
The Let-7 microRNA precursor gives rise to let-7, a microRNA (miRNA) involved in control of stem-cell division and differentiation. let-7, short for "lethal-7", was discovered along with the miRNA lin-4 in a study of developmental timing in C. elegans, making these miRNAs the first ever discovered. let-7 was later identified in humans as the first human miRNA , and is highly conserved across many species. Dysregulation of let-7 contributes to cancer development in humans by preventing differentiation of cells, leaving them stuck in a stem-cell like state. let-7 is therefore classified as a tumor suppressor.
The let-7 microRNA family refers to the many slight variations of let-7 that exist both within a single organism and across species. In humans, for example, there are ten unique let-7 family member sequences: let-7a through g, let-7i, mir-98, and mir-202.
In humans, mature let-7 acts via RNA-induced silencing by complexing with RISC and binding to target mRNA, preventing translation into protein. Known targets of let-7 include proteins related to the cell cycle and proliferation, such as MYC, RAS, cyclin D, HMGA2, and CDC25A. Knockdown of these proteins by let-7 prevents proliferation and induces differentiation of cells. Important inhibitors of let-7 include LIN28, which binds to let-7 directly, and the proto-oncogene MYC, which suppresses expression.