We previously described selective hypermethylation of the 5'-long terminal repeat (LTR) of HTLV-1 provirus in vivo and in vitro. This prompted us to analyze CpG methylation of the two LTRs of the HIV provirus in chronically infected cell lines. The results demonstrate selective hypermethylation of the 5' LTR of the HIV provirus in ACH-2 cells. Moreover, induction of viral gene expression by TNF-alpha resulted in demethylation of the 5'-LTR. These results suggest that selective epigenetic modification of the 5'LTR of the HIV-1 provirus may be an important mechanism by which proviral activity is suppressed.
Laboratory of Tumor Cell Biology, Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan. tishida@ims.u-tokyo.ac.jp
