Mir-7 microRNA precursor explained

mir-7 microRNA precursor
Symbol:	mir-7
Rfam:	RF00053
Mirbase:	MI0000263
Mirbase Family:	MIPF0000022
Rna Type:	Gene miRNA
Tax Domain:	Eukaryota

This family represents the microRNA (miRNA) precursor mir-7. This miRNA has been predicted or experimentally confirmed in a wide range of species.^[1] miRNAs are transcribed as ~70 nucleotide precursors (modelled here) and subsequently processed by the Dicer enzyme to give a ~22 nucleotide product. In this case the mature sequence comes from the 5' arm of the precursor. The extents of the hairpin precursors are not generally known and are estimated based on hairpin prediction. The involvement of Dicer in miRNA processing suggests a relationship with the phenomenon of RNA interference.

Mature miRNA-7 is derived from three microRNA precursors in the human genome, miR-7-1, miR-7-2 and miR-7-3. miRNAs are numbered based on the sequence of the mature RNA.

miR-7 is directly regulated by the transcription factor HoxD10.^[2]

miRNAs are thought to have regulatory roles through complementarity to mRNA.miR-7 is essential for the maintenance of regulatory stability under conditions of environmental flux.^[3] It plays an important role in controlling mRNA expression. The miR-7 gene is found in most sequenced Urbilateria species, and the sequence of its mature miRNA product is perfectly conserved from annelids to humans, indicating a strong functional conservation.^[3]

Targets of miR-7

Bioinformatic predictions suggest that the human EGFR mRNA 3'-untranslated region contains three microRNA-7 (miR-7) target sites, which are not conserved across mammals.^[4] In Drosophila photoreceptor cells, miR-7 controls epidermal growth factor receptor (EGFR) signaling and promotes photoreceptor differentiation.^[5] Among other targets of miR-7 are insulin-like growth factor 1 receptor (IGF1R) and PIK3CD,^[6] E(spl) gene family ^[7] and Pak1 (cancer cells).^[2] c-Fos is also a target of miR-7b in mice.^[8] Pax6 translation in the lateral wall of the subventricular zone of developed mice is post-transcriptionally regulated by miRNA-7a mediated gene silencing, which is necessary to control the rate of dopaminergic neuron production in the olfactory bulb.^[9]

Clinical relevance

Multiple roles and targets of miR-7 as well as its expression pattern were linked to regulatory mechanisms and pathogenesis in glioblastoma,^[10] breast cancer^[11] and other types of cancers,^{[4] [6] [12]} as well as in schizophrenia^[13] and visual abnormalities.^[14] Inhibition of the motility, invasiveness, anchorage-independent growth, and tumorigenic potential of highly invasive breast cancer cells through the introduction of miR-7 suggests a strong therapeutic potential of miR-7.^{[2] [15]}

Further reading

• Lagos-Quintana M, Rauhut R, Lendeckel W, Tuschl T . Identification of novel genes coding for small expressed RNAs . Science . 294 . 5543 . 853–8 . October 2001 . 11679670 . 10.1126/science.1064921 . 11858/00-001M-0000-0012-F65F-2 . 2001Sci...294..853L . 18101169 . free .
• Ambros V . microRNAs: tiny regulators with great potential . Cell . 107 . 7 . 823–6 . December 2001 . 11779458 . 10.1016/S0092-8674(01)00616-X . free .
• Chen H, Shalom-Feuerstein R, Riley J, Zhang SD, Tucci P, Agostini M, Aberdam D, Knight RA, Genchi G, Nicotera P, Melino G, Vasa-Nicotera M . miR-7 and miR-214 are specifically expressed during neuroblastoma differentiation, cortical development and embryonic stem cells differentiation, and control neurite outgrowth in vitro . Biochemical and Biophysical Research Communications . 394 . 4 . 921–7 . April 2010 . 20230785 . 10.1016/j.bbrc.2010.03.076 .
• Doxakis E . Post-transcriptional regulation of alpha-synuclein expression by mir-7 and mir-153 . The Journal of Biological Chemistry . 285 . 17 . 12726–34 . April 2010 . 20106983 . 2857101 . 10.1074/jbc.M109.086827 . free .
• Pek JW, Lim AK, Kai T . Drosophila maelstrom ensures proper germline stem cell lineage differentiation by repressing microRNA-7 . Developmental Cell . 17 . 3 . 417–24 . September 2009 . 19758565 . 10.1016/j.devcel.2009.07.017 . free .
• Junn E, Lee KW, Jeong BS, Chan TW, Im JY, Mouradian MM . Repression of alpha-synuclein expression and toxicity by microRNA-7 . Proceedings of the National Academy of Sciences of the United States of America . 106 . 31 . 13052–7 . August 2009 . 19628698 . 2722353 . 10.1073/pnas.0906277106 . 2009PNAS..10613052J . free .
• Correa-Medina M, Bravo-Egana V, Rosero S, Ricordi C, Edlund H, Diez J, Pastori RL . MicroRNA miR-7 is preferentially expressed in endocrine cells of the developing and adult human pancreas . Gene Expression Patterns . 9 . 4 . 193–9 . April 2009 . 19135553 . 10.1016/j.gep.2008.12.003 .

External links

• • Web site: MIR7-1 (microRNA 7-1) . Atlas of Genetics and Cytogenetics in Oncology and Haematology . Purow . Benjamin . December 2008.

Notes and References

1. Web site: miRNA gene family: mir-7 (92 sequences) . https://web.archive.org/web/20070929111655/http://microrna.sanger.ac.uk/cgi-bin/sequences/mirna_summary.pl?fam=MIPF0000022 . dead . 2007-09-29 . .
2. Reddy SD, Ohshiro K, Rayala SK, Kumar R . MicroRNA-7, a homeobox D10 target, inhibits p21-activated kinase 1 and regulates its functions . Cancer Research . 68 . 20 . 8195–200 . October 2008 . 18922890 . 3636563 . 10.1158/0008-5472.CAN-08-2103 .
3. Li X, Cassidy JJ, Reinke CA, Fischboeck S, Carthew RW . A microRNA imparts robustness against environmental fluctuation during development . Cell . 137 . 2 . 273–82 . April 2009 . 19379693 . 2674871 . 10.1016/j.cell.2009.01.058 .
4. Webster RJ, Giles KM, Price KJ, Zhang PM, Mattick JS, Leedman PJ . Regulation of epidermal growth factor receptor signaling in human cancer cells by microRNA-7 . The Journal of Biological Chemistry . 284 . 9 . 5731–41 . February 2009 . 19073608 . 10.1074/jbc.M804280200 . free .
5. Li X, Carthew RW . A microRNA mediates EGF receptor signaling and promotes photoreceptor differentiation in the Drosophila eye . Cell . 123 . 7 . 1267–77 . December 2005 . 16377567 . 10.1016/j.cell.2005.10.040 . free .
6. Jiang L, Liu X, Chen Z, Jin Y, Heidbreder CE, Kolokythas A, Wang A, Dai Y, Zhou X . MicroRNA-7 targets IGF1R (insulin-like growth factor 1 receptor) in tongue squamous cell carcinoma cells . The Biochemical Journal . 432 . 1 . 199–205 . November 2010 . 20819078 . 3130335 . 10.1042/BJ20100859 .
7. Stark A, Brennecke J, Russell RB, Cohen SM . Identification of Drosophila MicroRNA targets . PLOS Biology . 1 . 3 . E60 . December 2003 . 14691535 . 270017 . 10.1371/journal.pbio.0000060 . free .
8. Lee HJ, Palkovits M, Young WS . miR-7b, a microRNA up-regulated in the hypothalamus after chronic hyperosmolar stimulation, inhibits Fos translation . Proceedings of the National Academy of Sciences of the United States of America . 103 . 42 . 15669–74 . October 2006 . 17028171 . 1622879 . 10.1073/pnas.0605781103 . free .
9. 10.1038/nn.3142 . 15 . miR-7a regulation of Pax6 controls spatial origin of forebrain dopaminergic neurons . 2012 . Nature Neuroscience . 1120–1126 . de Chevigny A. 8 . 22729175 . 8456253 .
10. Kefas B, Godlewski J, Comeau L, Li Y, Abounader R, Hawkinson M, Lee J, Fine H, Chiocca EA, Lawler S, Purow B . microRNA-7 inhibits the epidermal growth factor receptor and the Akt pathway and is down-regulated in glioblastoma . Cancer Research . 68 . 10 . 3566–72 . May 2008 . 18483236 . 10.1158/0008-5472.CAN-07-6639 . free .
11. Foekens JA, Sieuwerts AM, Smid M, Look MP, de Weerd V, Boersma AW, Klijn JG, Wiemer EA, Martens JW . Four miRNAs associated with aggressiveness of lymph node-negative, estrogen receptor-positive human breast cancer . Proceedings of the National Academy of Sciences of the United States of America . 105 . 35 . 13021–6 . September 2008 . 18755890 . 2529088 . 10.1073/pnas.0803304105 . 2008PNAS..10513021F . free .
12. Veerla S, Lindgren D, Kvist A, Frigyesi A, Staaf J, Persson H, Liedberg F, Chebil G, Gudjonsson S, Borg A, Månsson W, Rovira C, Höglund M . MiRNA expression in urothelial carcinomas: important roles of miR-10a, miR-222, miR-125b, miR-7 and miR-452 for tumor stage and metastasis, and frequent homozygous losses of miR-31 . International Journal of Cancer . 124 . 9 . 2236–42 . May 2009 . 19127597 . 10.1002/ijc.24183 . free .
13. Perkins DO, Jeffries CD, Jarskog LF, Thomson JM, Woods K, Newman MA, Parker JS, Jin J, Hammond SM . microRNA expression in the prefrontal cortex of individuals with schizophrenia and schizoaffective disorder . Genome Biology . 8 . 2 . R27 . 2007 . 17326821 . 1852419 . 10.1186/gb-2007-8-2-r27 . free .
14. Arora A, McKay GJ, Simpson DA . Prediction and verification of miRNA expression in human and rat retinas . Investigative Ophthalmology & Visual Science . 48 . 9 . 3962–7 . September 2007 . 17724173 . 10.1167/iovs.06-1221 . free .
15. Czech MP . MicroRNAs as therapeutic targets . The New England Journal of Medicine . 354 . 11 . 1194–5 . March 2006 . 16540623 . 10.1056/NEJMcibr060065 .