Nuclear translocation and regulation of intranuclear distribution of cytoplasmic poly(A)-binding protein are distinct processes mediated by two Epstein Barr virus proteins.
Many viruses target cytoplasmic polyA binding protein (PABPC) to effect widespread inhibition of host gene expression, a process termed viral host-shutoff (vhs). During lytic replication of Epstein Barr Virus (EBV) we observed that PABPC was efficiently translocated from the cytoplasm to the nucleus. Translocated PABPC was diffusely distributed but was excluded from viral replication compartments. Vhs during EBV infection is regulated by the viral alkaline nuclease, BGLF5. Transfection of BGLF5 alone into BGLF5-KO cells or uninfected 293 cells promoted translocation of PAPBC that was distributed in clumps in the nucleus. ZEBRA, a viral bZIP protein, performs essential functions in the lytic program of EBV, including activation or repression of downstream viral genes. ZEBRA is also an essential replication protein that binds to viral oriLyt and interacts with other viral replication proteins. We report that ZEBRA also functions as a regulator of vhs. ZEBRA translocated PABPC to the nucleus, controlled the intranuclear distribution of PABPC, and caused global shutoff of host gene expression. Transfection of ZEBRA alone into 293 cells caused nuclear translocation of PABPC in the majority of cells in which ZEBRA was expressed. Co-transfection of ZEBRA with BGLF5 into BGLF5-KO cells or uninfected 293 cells rescued the diffuse intranuclear pattern of PABPC seen during lytic replication. ZEBRA mutants defective for DNA-binding were capable of regulating the intranuclear distribution of PABPC, and caused PABPC to co-localize with ZEBRA. One ZEBRA mutant, Z(S186E), was deficient in translocation yet was capable of altering the intranuclear distribution of PABPC. Therefore ZEBRA-mediated nuclear translocation of PABPC and regulation of intranuclear PABPC distribution are distinct events. Using a click chemistry-based assay for new protein synthesis, we show that ZEBRA and BGLF5 each function as viral host shutoff factors.
Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut, United States of America.
Richard
R
Park
Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, United States of America.
Ayman
A
El-Guindy
Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, United States of America.
Lee
L
Heston
Institute of Cancer Research, National Health Research Institutes, Zhunan Town, Taiwan.
Su-Fang
SF
Lin
Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, United States of America.
Kuan-Ping
KP
Yu
Program in Computational Biology and Bioinformatics, Yale University, New Haven, Connecticut, United States of America.
Mate
M
Nagy
Department of Biochemistry, Howard Hughes Medical Institute, University of Colorado Biofrontiers Institute, Boulder, Colorado, United States of America.
Sumit
S
Borah
Department of Tumor Virology, German Cancer Research Center, Heidelberg, Germany.
Henri-Jacques
HJ
Delecluse
Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut, United States of America.
Joan
J
Steitz
Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut, United States of America; Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, United States of America; Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut, United States of America.
George
G
Miller
D021581:Active Transport, Cell Nucleus; D002467:Cell Nucleus / Q000378:metabolism* / Q000821:virology; D002478:Cells, Cultured; D003851:Deoxyribonucleases / Q000502:physiology*; D020031:Epstein-Barr Virus Infections / Q000821:virology; D057809:HEK293 Cells; D004854:Herpesvirus 4, Human / Q000472:pathogenicity / Q000502:physiology; D054884:Host-Pathogen Interactions / Q000235:genetics; D006801:Humans; D039122:Poly(A)-Binding Protein I / Q000378:metabolism*; D014018:Tissue Distribution; D015534:Trans-Activators / Q000502:physiology*; D014764:Viral Proteins / Q000502:physiology*; D014779:Virus Replication / Q000235:genetics
C063676:BZLF1 protein, Herpesvirus 4, Human; D039122:Poly(A)-Binding Protein I; D015534:Trans-Activators; D014764:Viral Proteins; D003851:Deoxyribonucleases; C083203:deoxyribonuclease, Epstein-Barr virus