Stochastic Gene Expression in a Lentiviral Positive Feedback Loop: HIV-1   Tat Fluctuations Drive Phenotypic Diversity
  Stochastic gene expression has been implicated in a variety of cellular processes, including cell differentiation and disease. In this issue of Cell, Weinberger et al. (2005) take an integrated computational-experimental approach to study the Tat transactivation feedback loop in HIV-1 and show that fluctuations in a key regulator, Tat, can result in a phenotypic bifurcation. This phenomenon is observed in an isogenic population where individual cells display two distinct expression states corresponding to latent and productive infection by HIV-1. These findings demonstrate the importance of stochastic gene expression in molecular "decision-making." 
Leor S. Weinberger, John C. Burnett, Jared E. Toettcher, Adam P.   Arkin, and David V. Schaffer