College of Veterinary Medicine
Center for Retrovirus Research

Mechanisms of HTLV-1 p30 in Transcription and DNA Repair Replication and Lymphocyte Activation

Principal Investigator: Michael Lairmore, DVM, PhD, The Ohio State University

The role of HTLV-1 in mediating these diseases is related to the ability of the virus to evoke lymphocyte activation. This complex retrovirus encodes typical gag, pol and env gene products as well as unique regulatory and accessory genes encoded in pX ORF I-IV between the env gene and the 3' LTR. Emerging evidence indicates a critical role of the gene products encoded in pX ORF I and II in viral replication. Four proteins designated p12I, p27I, p13II and p30II are expressed from these highly conserved ORFs. p12I is a hydrophobic protein that localizes in the endoplasmic reticulum and has four minimal SH3 binding motifs. Using molecular clones of HTLV-1 with selective mutation of ORFs I and II, we were the first to identify functional roles of p12I and p13II/p30II in establishment of infection in vivo. Subsequently, we demonstrated a vital role on p12I in viral infectivity in quiescent lymphocytes and in enhancement of NFAT-mediated transcription. Thus, we are the first to demonstrate an essential role for p12I in early T-cell activation and have pioneered the examination of the role of these "accessory" proteins in viral replication in vivo and in lymphocyte activation, an important antecedent to virus transmission and cell transformation.

The focus of this project emerged from these studies and concentrates our proposed studies on p30 encoded in pX ORF II of HTLV-1. This nuclear/nucleolar protein has homology to transcription factors and contains G/SK consensus acetylation sites. Our collaborative studies have provided the first evidence that p30 is required by the virus to establish infection in animals, acts as a transcription factor, is positively influenced by acetylation and binds the KIX domain of the co-activator, p300. We now provide exciting new data that implicate p30 in DNA damage/repair signaling that results in cell cycle perturbation and likely promote viral integration. Our data indicate that HTLV-1 uses p30 in a novel manner to modulate the cellular environment to favor cell survival and balances the influence of viral transactivation (i.e., Tax) to allow viral persistence. In our next phase of this PPG, we provide interdependent approaches to identify the roles of HTLV-1 p30 and HTLV-2 p28 (Project 2) by comparative testing of essential transcriptional and post-transcriptional control parameters.

Specific aims addressed in our proposed research include: 1) Localize important Structural motifs of HTLV-1 p30 that mediated transcriptional regulation and DNA damage/repair signaling in T lymphocytes; 2) Determine the role of post-translation modifications in HTLV-1 p30 -mediated transcriptional regulation and DNA damage/repair signaling in T lymphocytes.; 3) Test structural motifs important in p30 mediated transcriptional regulation and DNA damage/repair signaling in the spatial and temporal distribution of early virus expression in rabbits with HTLV-1 molecular clones with selective mutations in pX ORF II. Our long-term goal is to understand how retroviruses, like HTLV-1 alter T cell physiology and thereby gain insight into mechanisms of the early phases of cell transformation.