ACC EPT

2 Recent research has emphasized the notion that HIV-1 latency is controlled by a restrictive histone code at, or DNA methylation of the integrated viral promoter (LTR). The present concept of HIV-1 latency has essentially been patterned from the principles of cellular 5 gene regulation. Here we introduce an experimental system that allows for the qualitative and quantitative kinetic study of latency establishment and maintenance at the population level. In this system, we find no evidence that HIV-1 latency establishment is the consequence of down regulation of initial active infection followed by the establishment of a restrictive histone code at the viral LTR. Latent infection was established following integration of the virus in the absence 10 of viral gene expression (silent integration) and was a function of the NF-κB activation level in the host cell at the time of infection. In the absence of a role for epigenetic regulation, we demonstrate that transcriptional interference, a mechanism that has recently been suggested to add to the stabilization of HIV-1 latency, is the primary mechanism to govern latency maintenance. These findings provide direct experimental evidence that the high number of viral 1