KAPOSI'S SARCOMA ASSOCIATED HERPES VIRUS ENCODED LANA PROTEIN REGULATES TELOMERE LENGTH

Meir Shamay ^1,3 Jianyong Liu ¹ Heng Zhu ^1,2 S. Diane Hayward ¹

¹Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland
²High Throughput Biology Center, Johns Hopkins University School of Medicine, Baltimore, Maryland
³Faculty of Medicine, Bar-Ilan University, Safed

Kaposi’s sarcoma associated herpesvirus (KSHV, HHV-8) is the etiological agent of several human malignancies including Kaposi’s sarcoma (KS), primary effusion lymphoma (PEL) and multicentric Castleman’s disease (MCD). The KSHV encoded LANA protein functions in latently infected cells as an essential participant in KSHV genome replication and as a driver of dysregulated cell growth. To identify novel LANA protein-cell protein interactions that could contribute to these activities, we performed a proteomic screen in which purified LANA protein was incubated with an array displaying 4,192 non-redundant human recombinant proteins. Sixty-one interacting cell proteins were consistently detected. Novel LANA interactions include RPA1, RPA2, TRF1 and RLIM. These proteins are known to regulate telomere function. TRF1 is a telomere repeat DNA binding protein, and accumulation of TRF1 leads to telomere shortening. RLIM is an E3 ubiquitin ligase that regulates TRF1 stability, and down regulation of RLIM leads to TRF1 accumulation and telomere shortening. As expected, co-transfection of TRF1 with RLIM results in marked decrease of TRF1 protein levels. Interestingly, we have found that LANA leads to RLIM degradation by the proteasome, and therefore abrogates the ability of RLIM to degrade TRF1. In addition, LANA expression reduced the association of RPA1 and RPA2 with the telomeres. Expression of LANA in endothelial cells leads to shorter telomeres compared to the matched control cells. Short telomeres were also detected in KSHV infected PEL cells. In KSHV infected cells, telomere shortening may be one more mechanism by which LANA contributes to the development of malignancy.