FAK nuclear export signal sequences

Abstract

Ubiquitously expressed focal adhesion kinase (FAK), a critical component in transducing signals from sites of cell contacts with extracellular matrix, was named after its typical localization in focal adhesions. A nuclear localization of FAK has been also reported and its scaffolding role in nucleus and requirement for p53 ubiquitination were only recently described. Whereas FAK nuclear localization signal (NLS) was found in F2 lobe of FERM domain, nuclear export signal (NES) sequences have not been yet determined. Here we demonstrate that FAK has two NES sequences, NES1 in F1 lobe of FERM domain and NES2 in kinase domain. Although, both NES1 and NES2 are evolutionary conserved, and present as well in FAK-related protein kinase Pyk2, only NES2 demonstrates full biological nuclear export activity.