Determining Ubiquitin Interactions used by the Novel v-IPS1 of Kaposi’s Sarcoma Herpesvirus to Block Innate Immunity 4353

Description Kaposi sarcoma-associated herpesvirus is the etiologic agent of Kaposi’s Sarcoma. KSHV has evolved many ways to control the immune response allowing for viral replication. We found that KSHV has a viral homologue of IPS-1, which is a protein required for the production of Type I IFN cytokine, and we have termed this viral IPS-1. IFN cytokines normally function to limit viral replication when a virus is detected by innate immunity. V-IPS1 expression leads to the blockage of c-IPS1, limiting IFN activation. Interestingly, the downstream signaling component, TRAF3, is stabilized when v-IPS1 is expressed. Our primary approach focused on mapping v-IPS1’s interaction with c-IPS1 by cotransfecting mutant fragments of c-IPS1 with v-IPS1 to observe the IFN response. Results indicated that the TRAF-interacting motif and PRO regions of c-IPS1 are vital for v-IPS1 to inhibit c-IPS1 function. Curiously, the CARD, TIM, and PRO domains of c-IPS1 individually were not required for v-IPS1. We also transfected HEK293T cells to overexpress ubiquitin K63 or K48 to identify which ubq pathway was involved. Prelim data show overexpression of K63 dampens v-IPS1’s effect on c-IPS1. Secondly, we aim to elucidate the relationship between TRAF3 and v-IPS1. We mapped TRAF3’s function on v-IPS1 by using chimeras of TRAF3 with TRAF5 or 2. Prelim data indicate that TRAF3’s RING finger is important for v-IPS1 processing its full length to active form and may be involved in v-IPS1’s blockage of c-IPS1 function. Topic Categories Viral Immunology (VIR)