Tag:AsLOV2(cNLS) is an engineered light-regulated nuclear localization signal that consists of the LOV2 flavin binding domain (including the carboxy-terminal Jα helix) of the Avena sativa Phototropin 1 (PT1) gene, into which a nuclear localization signal (NLS) has been introduced towards the C-terminal end of the Jα helix (MAAKRVKLD replaces EAAKELPDA). In the dark, the closed conformation of the LOV2 domain results in the NLS being allosterically blocked. Upon illumination with blue light, the α-helix unfolds, exposing the NLS and allowing import into the nucleus of a protein of interest to which Tag:AsLOV2(cNLS) is fused (PMID:26083500).