The Epstein–Barr virus (EBV) immediate-early transactivator BZLF1 plays a key role in switching EBV infection from the latent to the lytic form by stimulating the expression cascade of lytic genes; it also regulates the expression of several cellular genes. Recently, we reported that BZLF1 is expressed in primary human B cells early after EBV infection. To investigate whether this BZLF1 expression early after infection plays a role in the EBV-induced growth transformation of primary B cells, we generated BZLF1-knockout EBV and quantitatively evaluated its transforming ability compared with that of wild-type EBV. We found that the 50 % transforming dose of BZLF1-knockout EBV was quite similar to that of wild-type EBV. Established lymphoblastoid cell lines (LCLs) harbouring BZLF1-knockout EBV were indistinguishable from LCLs harbouring wild-type EBV in their pattern of latent gene expression and in their growth in vitro. Furthermore, the copy numbers of EBV episomes were very similar in the LCLs harbouring BZLF1-knockout EBV and in those harbouring wild-type EBV. These data indicate that disrupting BZLF1 expression in the context of the EBV genome, and the resultant inability to enter lytic replication, have little impact on the growth of LCLs and the steady-state copy number of EBV episomes in established LCLs.
AdamsonA. L.,
KenneyS.1999; The Epstein–Barr virus BZLF1 protein interacts physically and functionally with the histone acetylase CREB-binding protein. J Virol 73:6551–6558
ChangY. N.,
DongD. L.,
HaywardG. S.,
HaywardS. D.1990; The Epstein–Barr virus Zta transactivator: a member of the bZIP family with unique DNA-binding specificity and a dimerization domain that lacks the characteristic heptad leucine zipper motif. J Virol 64:3358–3369
CohenJ. I.,
WangF.,
MannickJ.,
KieffE.1989; Epstein–Barr virus nuclear protein 2 is a key determinant of lymphocyte transformation. Proc Natl Acad Sci U S A 86:9558–9562[CrossRef]
CountrymanJ.,
MillerG.1985; Activation of expression of latent Epstein–Barr herpesvirus after gene transfer with a small cloned subfragment of heterogeneous viral DNA. Proc Natl Acad Sci U S A 82:4085–4089[CrossRef]
FarrellP. J.,
RoweD. T.,
RooneyC. M.,
KouzaridesT.1989; Epstein–Barr virus BZLF1 trans -activator specifically binds to a consensus AP-1 site and is related to c-fos. EMBO J 8:127–132
FeederleR.,
KostM.,
BaumannM.,
JanzA.,
DrouetE.,
HammerschmidtW.,
DelecluseH. J.2000; The Epstein–Barr virus lytic program is controlled by the co-operative functions of two transactivators. EMBO J 19:3080–3089[CrossRef]
FeederleR.,
NeuhierlB.,
BannertH.,
GeletnekyK.,
Shannon-LoweC.,
DelecluseH. J.2007; Epstein–Barr virus B95.8 produced in 293 cells shows marked tropism for differentiated primary epithelial cells and reveals interindividual variation in susceptibility to viral infection. Int J Cancer 121:588–594[CrossRef]
FlemingtonE. K.,
BorrasA. M.,
LytleJ. P.,
SpeckS. H.1992; Characterization of the Epstein–Barr virus BZLF1 protein transactivation domain. J Virol 66:922–929
HsuD. H.,
de Waal MalefytR.,
FiorentinoD. F.,
DangM. N.,
VieiraP.,
de VriesJ.,
SpitsH.,
MosmannT. R.,
MooreK. W.1990; Expression of interleukin-10 activity by Epstein–Barr virus protein BCRF1. Science 250:830–832[CrossRef]
HummeS.,
ReisbachG.,
FeederleR.,
DelecluseH. J.,
BoussetK.,
HammerschmidtW.,
SchepersA.2003; The EBV nuclear antigen 1 (EBNA1) enhances B cell immortalization several thousandfold. Proc Natl Acad Sci U S A 100:10989–10994[CrossRef]
ImaiS.,
NishikawaJ.,
TakadaK.1998; Cell-to-cell contact as an efficient mode of Epstein–Barr virus infection of diverse human epithelial cells. J Virol 72:4371–4378
IwakiriD.,
TakadaK.2004; Phosphatidylinositol 3-kinase is a determinant of responsiveness to B cell antigen receptor-mediated Epstein–Barr virus activation. J Immunol 172:1561–1566[CrossRef]
JonesR. J.,
SeamanW. T.,
FengW. H.,
BarlowE.,
DickersonS.,
DelecluseH. J.,
KenneyS. C.2007b; Roles of lytic viral infection and IL-6 in early versus late passage lymphoblastoid cell lines and EBV-associated lymphoproliferative disease. Int J Cancer 121:1274–1281[CrossRef]
KayeK. M.,
IzumiK. M.,
KieffE.1993; Epstein–Barr virus latent membrane protein 1 is essential for B-lymphocyte growth transformation. Proc Natl Acad Sci U S A 90:9150–9154[CrossRef]
KelleherC. A.,
PatersonR. K.,
DreyfusD. H.,
StreibJ. E.,
XuJ. W.,
TakaseK.,
JonesJ. F.,
GelfandE. W.1995; Epstein–Barr virus replicative gene transcription during de novo infection of human thymocytes: simultaneous early expression of BZLF-1 and its repressor RAZ. Virology 208:685–695[CrossRef]
KieffE.,
RickinsonA. B.2007; Epstein–Barr virus and its replication. In Fields Virology , 5th edn. pp 2603–2654Edited byKnipeD. M.,
HowleyP. M.
Philadelphia, PA: Lippincott Williams & Wilkins;
LiebermanP. M.,
BerkA. J.1991; The Zta trans-activator protein stabilizes TFIID association with promoter DNA by direct protein–protein interaction. Genes Dev 5:2441–2454[CrossRef]
LiebermanP. M.,
BerkA. J.1994; A mechanism for TAFs in transcriptional activation: activation domain enhancement of TFIID–TFIIA – promoter DNA complex formation. Genes Dev 8:995–1006[CrossRef]
MahotS.,
SergeantA.,
DrouetE.,
GruffatH.2003; A novel function for the Epstein–Barr virus transcription factor EB1/Zta: induction of transcription of the hIL-10 gene. J Gen Virol 84:965–974[CrossRef]
MannickJ. B.,
CohenJ. I.,
BirkenbachM.,
MarchiniA.,
KieffE.1991; The Epstein–Barr virus nuclear protein encoded by the leader of the EBNA RNAs is important in B-lymphocyte transformation. J Virol 65:6826–6837
MaruoS.,
YangL.,
TakadaK.2001; Roles of Epstein–Barr virus glycoproteins gp350 and gp25 in the infection of human epithelial cells. J Gen Virol 82:2373–2383
MaruoS.,
WuY.,
IshikawaS.,
KandaT.,
IwakiriD.,
TakadaK.2006; Epstein–Barr virus nuclear protein EBNA3C is required for cell cycle progression and growth maintenance of lymphoblastoid cells. Proc Natl Acad Sci U S A 103:19500–19505[CrossRef]
MauserA.,
Holley-GuthrieE.,
SimpsonD.,
KaufmannW.,
KenneyS.2002a; The Epstein–Barr virus immediate-early protein BZLF1 induces both a G2 and a mitotic block. J Virol 76:10030–10037[CrossRef]
MauserA.,
Holley-GuthrieE.,
ZanationA.,
YarboroughW.,
KaufmannW.,
KlingelhutzA.,
SeamanW. T.,
KenneyS.2002b; The Epstein–Barr virus immediate-early protein BZLF1 induces expression of E2F-1 and other proteins involved in cell cycle progression in primary keratinocytes and gastric carcinoma cells. J Virol 76:12543–12552[CrossRef]
NanboA.,
SugdenA.,
SugdenB.2007; The coupling of synthesis and partitioning of EBV's plasmid replicon is revealed in live cells. EMBO J 26:4252–4262[CrossRef]
RodriguezA.,
JungE. J.,
YinQ.,
CayrolC.,
FlemingtonE. K.2001; Role of c-myc regulation in Zta-mediated induction of the cyclin-dependent kinase inhibitors p21 and p27 and cell growth arrest. Virology 284:159–169[CrossRef]
ScalaG.,
QuintoI.,
RuoccoM. R.,
ArcucciA.,
MallardoM.,
CarettoP.,
ForniG.,
VenutaS.1990; Expression of an exogenous interleukin 6 gene in human Epstein–Barr virus B cells confers growth advantage and in vivo tumorigenicity. J Exp Med 172:61–68[CrossRef]
ShimizuN.,
Tanabe-TochikuraA.,
KuroiwaY.,
TakadaK.1994; Isolation of Epstein–Barr virus (EBV)-negative cell clones from the EBV-positive Burkitt's lymphoma (BL) line Akata: malignant phenotypes of BL cells are dependent on EBV. J Virol 68:6069–6073
StuartA. D.,
StewartJ. P.,
ArrandJ. R.,
MackettM.1995; The Epstein–Barr virus encoded cytokine viral interleukin-10 enhances transformation of human B lymphocytes. Oncogene 11:1711–1719
TakadaK.,
ShimizuN.,
SakumaS.,
OnoY.1986; trans activation of the latent Epstein–Barr virus (EBV) genome after transfection of the EBV DNA fragment. J Virol 57:1016–1022
TakadaK.,
HorinouchiK.,
OnoY.,
AyaT.,
OsatoT.,
TakahashiM.,
HayasakaS.1991; An Epstein–Barr virus-producer line Akata: establishment of the cell line and analysis of viral DNA. Virus Genes 5:147–156[CrossRef]
TosatoG.,
TannerJ.,
JonesK. D.,
RevelM.,
PikeS. E.1990; Identification of interleukin-6 as an autocrine growth factor for Epstein–Barr virus-immortalized B cells. J Virol 64:3033–3041
WenW.,
IwakiriD.,
YamamotoK.,
MaruoS.,
KandaT.,
TakadaK.2007; Epstein–Barr virus BZLF1 gene, a switch from latency to lytic infection, is expressed as an immediate-early gene after primary infection of B lymphocytes. J Virol 81:1037–1042[CrossRef]
WuF. Y.,
ChenH.,
WangS. E.,
ApRhysC. M.,
LiaoG.,
FujimuroM.,
FarrellC. J.,
HuangJ.,
HaywardS. D.,
HaywardG. S.2003; CCAAT/enhancer binding protein α interacts with ZTA and mediates ZTA-induced p21CIP-1 accumulation and G1 cell cycle arrest during the Epstein–Barr virus lytic cycle. J Virol 77:1481–1500[CrossRef]
WuY.,
MaruoS.,
YajimaM.,
KandaT.,
TakadaK.2007; Epstein–Barr virus (EBV)-encoded RNA 2 (EBER2) but not EBER1 plays a critical role in EBV-induced B-cell growth transformation. J Virol 81:11236–11245[CrossRef]
YokoiT.,
MiyawakiT.,
YachieA.,
KatoK.,
KasaharaY.,
TaniguchiN.1990; Epstein–Barr virus-immortalized B cells produce IL-6 as an autocrine growth factor. Immunology 70:100–105
YoshiyamaH.,
ImaiS.,
ShimizuN.,
TakadaK.1997; Epstein–Barr virus infection of human gastric carcinoma cells: implication of the existence of a new virus receptor different from CD21. J Virol 71:5688–5691
ZhangQ.,
GutschD.,
KenneyS.1994; Functional and physical interaction between p53 and BZLF1: implications for Epstein–Barr virus latency. Mol Cell Biol 14:1929–1938