Herpes virus proteins ICP0 and BICP0 can activate NF-nB by catalyzing InBa ubiquitination Lirong Diao a,b , Bianhong Zhang a , Junkai Fan a , Xiang Gao a , Shaogang Sun a , Kai Yang a , Dan Xin b , Naihe Jin a , Yunqi Geng b , Chen Wang a, * a Laboratory of Molecular and Cellular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Box 49, 320 Yue Yang Road, Shanghai 200031, P.R. China b College of Life Science, Nan Kai University, Tianjin 300071, P.R. China Received 4 July 2004; received in revised form 12 July 2004; accepted 12 July 2004 Available online 25 August 2004 Abstract The immediate early proteins ICP0 and BICP0 from Herpes virus are promiscuous activators of both viral and cellular genes and play a critical role in virus life cycle. Here we report that ICP0 and BICP0 could induce NF-nB translocation from cytoplasm into nucleus and strongly activate NF-nB responsive genes specifically. This process was dependent on the RING domain of both proteins. In addition, ICP0 interacted specifically with InBa and its activating effect was attenuated by Ubch5A(C85A) and MG132, but not by InBa(S32A/S36A). Remarkably, InBa was poly-ubiquitinated by both ICP0 and BICP0, in vitro and in vivo. These data indicate that ICP0 and BICP0, functioning as ubiquitin ligases, are bona fide activators of NF-nB signaling pathway. Our study identifies a new way ICP0 and BICP0 explore to regulate gene expression. D 2004 Elsevier Inc. All rights reserved. Keywords: Herpes virus; ICP0; BICP0; Ubiquitin; InBa 1. Introduction Herpes simplex viruses (HSV) are nuclearly replicating, icosahedral, enveloped DNA viruses. They are the culprits of cold sores and other more serious diseases [1]. HSV-1 has developed a successful strategy to establish a life-long latent infection in the nervous system after initial entry into the epithelial cells [2]. In response to stress, it can reactivate into lytic cycle and express the immediate-early genes such as ICP0 , ICP4 , ICP27, which then turn on the early and late genes [3]. Remarkably, HSV-1 functional counterpart in bovine has been characterized as bovine herpes virus 1 (BHV-1) that shares a number of biological properties with HSV-1 in terms of life cycle and protein functions [4]. ICP0 is a 775-amino-acid multifunctional protein that is expressed immediately after HSV-1 infection or reactivation [5]. It is critical for the efficient initiation of lytic infection and sufficient to induce HSV-1 reactivation from neuronal latency [6]. The underlying mechanisms have been under intensive study. Initially, ICP0 was found to promote both viral and cellular protein production by stimulating mRNA synthesis [7]. However, it failed to identify signature promoter sequence recognized by ICP0; nor was it able to demonstrate any affinity between ICP0 and DNA, which suggested that the mode of ICP0 action was not a simple case of direct transcriptional activation [5]. This conjecture was partly substantiated by the observation that ICP0 co- localized with the nuclear substructures called ND10 and mediated the disruption of them [8–10]. Recently, ICP0 was shown to interact specifically with a diverse collection of proteins including USP7, cyclin D3, elongation factor EF- 1y, transcription factor BMAL1 and HSV-1 ICP4 [11–15]. Importantly, ICP0 contains a RING domain at its N- 0898-6568/$ - see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.cellsig.2004.07.003 * Corresponding author. Tel.: +86 21 54921185. E-mail addresses: yqgeng@public.tpt.tj.cn (Y. Geng)8 cwang01@sibs.ac.cn (C. Wang). Cellular Signalling 17 (2005) 217 – 229 www.elsevier.com/locate/cellsig