Fig 8.

Tat-dependent reactivation of silent proviruses upon coinfection. (A) Target cell incubation with HIV-1 reporters can lead to reporter gene expression or silent infection. When cells are incubated with two distinct viruses, the status of each provirus can be calculated based on stochastic infection. (B) In the absence of cross talk between the GFP and DsRed proviruses (left pie chart), reporter expression takes place only in cells that harbor a provirus with a productive-infection status. In the case of transactivation (right pie chart), proviruses with a productive-infection status can rescue silent proviruses, leading to the expression of both reporter genes. Depending on the strength of transactivation, silent GFP and DsRed proviruses might also transactivate each other and drive the expression of both reporter genes. In this example, single incubation results in 33% reporter-positive cells and 33% infected yet reporter-negative cells. The latter percentage can be estimated with the model described in Materials and Methods from coinfection experiments that result in 44% GFP- and DsRed-positive cells.