Poster abstracts
Poster number 27 submitted by Taiwei Li
The host protein SAMHD1 interacts with the HIV-1 promoter to suppress viral transcription
Tai-Wei Li (Molecular, Cellular and Developmental Biology Graduate Program,Ohio State University), Jenna M. Antonucci (Department of Microbiology, Ohio State University), Corine St. Gelais (Center for Retrovirus Research,Ohio State University), Li Wu (Center for RNA Biology, The Ohio State University,)
Abstract:
SAM domain and HD domain-containing protein 1 (SAMHD1) is a novel intracellular deoxynucleotide triphosphohydrolase (dNTPase). Through its dNTPase function, SAMHD1 maintains low dNTP levels in non-dividing immune cells to restrict reverse transcription of human immunodeficiency virus type 1 (HIV-1). However, in activated CD4+ T-cells, where SAMHD1 dNTPase is less active during cell proliferation, HIV-1 can establish productive infection and integrate its proviral genome into the chromosome. Transcriptionally silent HIV-1 provirus is maintained in CD4+ T-cells, which differentiate into memory T-cells and serve as the major latent reservoir of HIV-1. We have shown that SAMHD1 suppresses NF-κB signaling during HIV-1 infection. NF-κB signaling is important to reactivate the latent HIV-1 provirus. During reactivation, the HIV-1 long term repeat (LTR) promoter binds host transcription factors such as NF-κB to initiate transcription of viral mRNA for viral protein synthesis. We hypothesize that SAMHD1 suppresses HIV-1 LTR-driven gene transcription by disrupting binding of NF-κB (p100/p52/p50) to the LTR. SAMHD1 may also suppress the translocation of additional transcription factors from the cytoplasm or directly disrupt the transcription initiation of RNA polymerase II complex in the nucleus. To investigate how SAMHD1 suppresses the HIV-1 LTR function, we will analyze the activity of LTR-driven luciferase reporter constructs in 293T cells with co-expression of nuclear-localized wild-type (WT) SAMHD1 or cytoplasmic mutant SAMHD1 with deletion of nuclear localization signal (ΔNLS). To further delineate the mechanism in CD4+ T cells, WT or ΔNLS SAMHD1 will be expressed in an HIV-1 latently infected J-Lat cell line for reactivation assays. J-Lat cells contain the HIV-1 provirus harboring a green fluorescent protein (GFP) gene that is expressed after treatment with latency reversing agents. We will analyze HIV-1 reactivation by measuring GFP and HIV-1 gag mRNA levels. Through this study, we will better understand SAMHD1’s contribution to maintenance of viral latency in infected cells.
Keywords: SAMHD1, HIV-1, viral transcription