Downloaded from www.microbiologyresearch.org by IP: 54.87.0.57 On: Mon, 12 Jun 2017 23:41:48 Journal of General Virology (2000), 81, 2645–2652. Printed in Great Britain ................................................................................................................................................................................................................................................................................... Latency-associated nuclear antigen of Kaposi’s sarcoma- associated herpesvirus (human herpesvirus-8) binds ATF4/CREB2 and inhibits its transcriptional activation activity Chunghun Lim, Hekwang Sohn, Yousang Gwack and Joonho Choe Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Taejeon 305-701, Korea Latency-associated nuclear antigen (LANA), encoded by ORF 73 of Kaposi’s sarcoma-associated herpesvirus (KSHV ; human herpesvirus-8), may play an important role in the persistence of the viral episome by tethering it to host chromosomes during mitosis. It also has been suggested from its amino acid sequence features that LANA may have transcription-regulatory activity. Here, it is reported that LANA interacts with activating transcription factor (ATF) 4/cAMP response element- binding protein (CREB) 2, a member of the ATF/CREB family of transcription factors, and represses the transcriptional activation activity of ATF4/CREB2. Repression by LANA is independent of the DNA-binding ability of ATF4/CREB2, since LANA also represses transactivation of ATF4/CREB2 fused to the GAL4 DNA-binding domain and does not affect the DNA-binding ability of ATF4/CREB2 in an electrophoretic mobility shift assay. The putative leucine zipper domain of LANA is required for binding to the relatively conserved basic region/leucine zipper domain (bZIP) of ATF4/CREB2, suggesting that the interaction may involve leucine zipper dimerization. Introduction Kaposi’s sarcoma-associated herpesvirus (KSHV), also called human herpesvirus-8, is the likely aetiological agent of Kaposi’s sarcoma (KS), the most common AIDS-related malignancy (Chang et al., 1994 ; Moore & Chang, 1995). KSHV also has been implicated in several B-cell lymphoproliferative diseases, including primary effusion lymphoma (PEL) (Cesarman et al., 1995), formerly designated body cavity-based lymphoma (BCBL), and some cases of multicentric Castleman’s disease (Soulier et al., 1995). KSHV establishes a latent infection in KS spindle cells, as well as PELBCBL cell lines. Among the viral genes expressed in the latent state, latency-associated nuclear antigen (LANA), encoded by ORF 73 of the KSHV genome, is a 222–234 kDa nuclear protein consisting of 1162 amino acids (Russo et al., 1996 ; Rainbow et al., 1997). It may be involved in the latent replication of the viral genome during mitosis of host cells by tethering the viral episome to host chromosomes (Ballestas et al., 1999 ; Cotter & Robertson, 1999). As deduced from its amino acid sequence, LANA may also possess transcription-regulatory activity (Russo et al., Author for correspondence : Joonho Choe. Fax 82 42 869 5630. e-mail jchoemail.kaist.ac.kr 1996 ; Ganem, 1997 ; Cotter & Robertson, 1999). Recently, several cellular proteins have been shown to interact with LANA. These cellular proteins include histone H1 (Cotter & Robertson, 1999), RING3 (Platt et al., 1999) and p53 (Friborg et al., 1999). We performed a yeast two-hybrid assay with full-length LANA as bait to identify cellular proteins that interact with LANA. Among several positive clones was a partial cDNA of activating transcription factor (ATF) 4 (Hai et al., 1989), also called cAMP response element (CRE)-binding protein (CREB) 2 (Karpinski et al., 1992) or TAXREB67 (Tsujimoto et al., 1991), which is a member of the ATFCREB family of transcription factors. ATF4CREB2 was initially characterized as a negative regulatory transcription factor of CRE (Karpinski et al., 1992). It was later shown to interact with CREB-binding protein (CBP)p300 co-activators as well as several general tran- scription factors, including TATA-binding protein, TFIIB and the RAP30 subunit of TFIIF, and it functions as a transcriptional activator (Liang & Hai, 1997). Members of the ATFCREB family of transcription factors share a relatively conserved basic regionleucine zipper (bZIP) domain required for direct contact with DNA and homo- and heterodimerization (Sassone-Corsi, 1995). They also dimerize selectively with the FosJun family of transcription factors (Hai & Curran, 1991). 0001-7100  2000 SGM CGEF