Project 1

Mechanisms of p12 and p30 in HTLV
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. We hypothesize that p12I serves a critical role in viral replication during early stages of the virus infection by altering calcium-dependent NFAT-mediated transcription. In parallel, we report that the nuclear localizing p30II differentially modulates CRE-and TRE-mediated transcription through CBP/p300.

We hypothesize that p30II influences viral and cellular CRE-mediated transcription through the KIX domain of CBP/p300 to enhance virus expression. As a result of these studies, our laboratory is in a unique position to test mechanisms by which these “accessory” proteins influence HTLV-1 replication and cellular gene expression. Specific aims addressed in our proposed research include: 1) Determine structural motifs of p12I important in infection of quiescent T-cells and their influence in NFAT-mediated transcription; 2) Characterize the interaction of p30II with the co-activators, p300/CBP, and test the role of acetylation in p30II-mediated transcriptional activity and the influence of p30II in apoptosis; 3) Test the effects of HTLV-1 p12I, p30II, and Rex in virus expression in vivo by infecting rabbits with molecular clones with selective mutations in p12I and p30II-encoding pX gene regions. Our long-term goal is to understand the role of p12I, p30II, and Rex in the establishment of HTLV-1 infection in vivo.