Larcher Clara, Bernhard David, Schaadt Eveline, Adler Barbara, Ausserlechner Michael J, Mitterer Manfred, Huemer Hartwig P
Institute of Hygiene and Social Medicine, University of Innsbruck, Austria.
Haematologica. 2003 Dec;88(12):1324-35.
The role of carboxyterminal deletions of the latent membrane protein-1 (LMP1) in Epstein-Barr virus (EBV) infection and oncogenesis is unclear. Here we describe functional properties of a rare 69-bp LMP1 deletion mutant (LMP1(69del)) isolated from a patient with polyclonal B-cell lymphocytosis.
Colony focus assay was used to evaluate the transforming capacity of LMP1(69del) in comparison to that of wild-type LMP1 from EBV strain B95/8. Transient transfectants of B-, T-, epithelial and 3T3 cells, and stable transfectants with ecdysone-inducible LMP1 expression were produced. The signaling capacity of both LMP1s on nuclear transcription factors NFkappaB and AP-1 were studied. Secretion of matrix metalloproteinase MMP-9, apoptosis, and EBV lytic and latent gene expression were also investigated.
LMP(69del) showed transforming properties comparable to those of the wild-type oncoprotein. Induction of NFkappaB but a markedly reduced influence on AP-1 were observed. Both oncoproteins induced secretion of MMP-9, and enhanced pre-apoptotic effects in Jurkat-T cells leading to increased Fas/Apo-1 and doxorubicin-mediated apoptosis. Furthermore, LMP1(69del) showed a more effective down-regulation of the EBV lytic cycle master gene BZLF1(Zebra) than did wild-type LMP1.
(i) LMP1(69del) possesses oncogenic properties, (ii) the observed impaired activity on AP-1 does not interfere with MMP-9 induction, (iii) the enhanced inhibition of BZLF1 could compensate for previously described mutations of our isolate leading to a more lytic phenotype and may be responsible for counteracting permanent virus replication in the chronic active EBV syndrome observed in this patient.
潜伏膜蛋白1（LMP1）的羧基末端缺失在爱泼斯坦-巴尔病毒（EBV）感染及肿瘤发生中的作用尚不清楚。在此，我们描述了从一名多克隆B细胞淋巴细胞增多症患者分离出的罕见69bp LMP1缺失突变体（LMP1(69del)）的功能特性。
采用集落形成试验评估LMP1(69del)与EBV B95/8株野生型LMP1相比的转化能力。构建了B细胞、T细胞、上皮细胞和3T3细胞的瞬时转染体，以及具有蜕皮激素诱导LMP1表达的稳定转染体。研究了两种LMP1对核转录因子NFκB和AP-1的信号传导能力。还研究了基质金属蛋白酶MMP-9的分泌、细胞凋亡以及EBV裂解和潜伏基因表达。
LMP(69del)表现出与野生型癌蛋白相当的转化特性。观察到其可诱导NFκB，但对AP-1的影响明显降低。两种癌蛋白均诱导MMP-9分泌，并增强Jurkat-T细胞中的促凋亡前效应，导致Fas/Apo-1和阿霉素介导的细胞凋亡增加。此外，与野生型LMP1相比，LMP1(69del)对EBV裂解周期主基因BZLF1（Zebra）的下调作用更有效。
（i）LMP1(69del)具有致癌特性；（ii）观察到的对AP-1活性受损并不影响MMP-9的诱导；（iii）对BZLF1的增强抑制作用可能补偿了我们分离株先前描述的导致更裂解表型的突变，并可能是该患者慢性活动性EBV综合征中对抗病毒永久复制的原因。
