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Simian immunodeficiency virus (SIV) infection of natural hosts is characterized by nonpathogenic chronic viremia, maintenance of gastrointestinal epithelial barrier integrity, and low numbers of target cells. Assessment of cell-associated virus load in T cell subsets in multiple anatomic compartments of chronically SIV-infected sabeus African green monkeys (AGMs) revealed that gastrointestinal memory CD4 + T lymphocytes are a major source of cell-associated virus and a significant contributor to SIV viremia in AGMs.

INTRODUCTIONRegulating protein stability using small molecules provides a rapid, reversible, and tunable method to study a protein of interest’s (POI) role in cells. We recently designed a small protein domain based on the 12-kDa FKBP (FK506 binding protein) that can be fused at either the carboxyl or amino terminus of a protein of interest. This destabilization domain (DD) confers instability to fusion protein partners. The method described here explains how to use a DD fusion to control the biological activity of a POI. In the absence of a small molecule ligand, the DD is unstable and directs the fusion protein for degradation. Addition of the ligand stabilizes the DD, allowing the fusion protein to accumulate in cells and the POI to exert its biological effect. The ligand is specific for the DD and has no detectable off-target effects. By utilizing the specificity of genetic fusion and the speed of small molecule binding, this technique provides an alternative to RNA interference to study a POI’s role in cells.