A novel CRM1-dependent nuclear export signal in adenoviral E1A protein regulated by phosphorylation.
Adenoviral E1A is a versatile protein that can reprogram host cells for efficient viral replication. The nuclear import of E1A is mediated by a nuclear localization signal; however, whether E1A can be actively exported from the nucleus is unknown. We first reported a CRM1-dependent nuclear export signal (NES) in E1A that is conserved in the group C adenoviruses. We showed that CRM1 and E1A coimmunoprecipitated and that blockage of CRM1 function by leptomycin B or small interfering RNA resulted in the nuclear localization of E1A. Through mutational analyses, we identified an active canonical NES element within the E1A protein spanning amino acids 70-80. We further demonstrated that phosphorylation of adjacent serine (S)89 resulted in the cytoplasmic accumulation of E1A. Interestingly, coincident with the accumulation of cells in the S/G2/M phase and histone H1 phosphorylation, E1A was relocated to the cytoplasm at the late stage of the viral cycle, which was blocked by the CDC2/CDK2 inhibitor roscovitine. Importantly, titration of the progenies of the viruses in infected cells showed that the replication efficiency of the NES mutant adenovirus was up to 500-fold lower than that of the wild-type adenovirus. Collectively, our data demonstrate the existence of a NES in E1A that is modulated by the phosphorylation of the S89 residue and the NES plays a role for an efficient viral replication in the host cells.
Jiang
Hong
H
Department of Neuro-Oncology, Unit 1002, Brain Tumor Center, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA. hjiang@mdanderson.org
Olson
Melissa V
MV
Medrano
Diana R
DR
Lee
Ok-Hee
OH
Xu
Jing
J
Piao
Yuji
Y
Alonso
Marta M
MM
Gomez-Manzano
Candelaria
C
Hung
Mien-Chie
MC
Yung
W K Alfred
WK
Fueyo
Juan
J
D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D017500:Adenovirus E1A Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites; D002460:Cell Line; D006801:Humans; D028884:Karyopherins / Q000737:chemistry / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation; D021381:Protein Transport; D011687:Purines; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000378:metabolism*; D000077546:Roscovitine; D014779:Virus Replication; D000097606:Exportin 1 Protein
D017500:Adenovirus E1A Proteins; D028884:Karyopherins; D011687:Purines; D018160:Receptors, Cytoplasmic and Nuclear; D000077546:Roscovitine; D000097606:Exportin 1 Protein