Two nuclear export signals of Cdc6 are differentially associated with CDK-mediated phosphorylation residues for cytoplasmic translocation

摘要: Cdc6 is cleaved at residues 442 and 290 by caspase-3 during apoptosis producing p49-tCdc6 p32-tCdc6, respectively. While p32-tCdc6 unable to translocate into the cytoplasm, retains cytoplasmic translocation activity, but it has a lower efficiency than wild-type Cdc6. We hypothesized that novel nuclear export signal (NES) sequence exists between amino acids 442. contains NES in region of 300-315 (NES2) shares similarity with NES1 462-476. In mutant versions Cdc6, we replaced leucine alanine NES2 co-expressed constructs cyclin A. observed these mutants was reduced comparison Moreover, which all four were mutated significantly inhibited The Crm1 binding activities consistent its translocation. Further studies have revealed L468 L470 are required for phosphorylated S74, while L311 L313 accelerate S54. These results suggest two NESs work cooperatively distinctly S74 S54 A/Cdk2.