In molecular biology mir-657 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
Lv K, Guo Y, Zhang Y, Wang K, Jia Y, Sun S (September 2008). "Allele-specific targeting of hsa-miR-657 to human IGF2R creates a potential mechanism underlying the association of ACAA-insertion/deletion polymorphism with type 2 diabetes". Biochemical and Biophysical Research Communications. 374 (1): 101–5. doi:10.1016/j.bbrc.2008.06.102. PMID18602895.