**7. Functions of miRNAs in nucleotide excision repair (NER)**

NER recognizes bulky, helix distorting defects, such as cross-linking thymine dimmers. NER is particularly important for removing the vast majority of UV-induced DNA damage. Currently, only one miRNA is reported to be related with NER (Crosby et al., 2009). miR-373 suppresses the expression of a NER protein called RAD23B. RAD23B is a key component of the XPC/RAD23B complex that mediates damage recognition in the NER pathway (Batty et al., 2000). NER activity is functionally reduced in hypoxic cells (Yuan et al., 2000). A possible mechanism for the hpoxia-induced down-regulation of RAD23B is that hpoxia can upregulate miR-373 expression, and the up-regulated miR-373 then suppresses RAD23B expression. This mechanism was supported by the fact that pre-treating cells with anti-miR-373 reversed the hypoxia-mediated down-regulation of RAD23B in hypoxic cells (Crosby, et al., 2009).
