The activation domain of Tat is required for the interaction with PRMT6. (A) Upper panel, scale representation of the two exon-encoded HIV-1 Tat protein showing amino acid positions 1 and 101, functional domains (italicized text) and structural regions (bold text) as defined by . ARM, arginine rich motif; Aux., auxiliary region. Lower panel, scale representations of FLAG epitope-tagged Tat (Tat-FLAG) protein and derivative domain deletion mutants. The numbers above each schema represent the amino acid boundaries of the domain deletions. The carboxyl-terminal FLAG epitope tag is represented as a vertical bar. (B) Interactions between Myc epitope-tagged PRMT6 (Myc-PRMT6) and wild type or domain deleted Tat-FLAG as determined by immunoprecipitation. HeLa cells were transfected to express Myc-PRMT6 with either wild type Tat-FLAG (WT) or a domain deletion mutant of Tat-FLAG. Immunoprecipitations were performed on lysates prepared from transfected cells using anti-FLAG agarose beads (αFLAG IP). Cell lysates (left panel) and immunoprecipitates (right panel) were western blotted using anti-Myc and anti-FLAG antibodies. Loading of cell lysates was normalized for equal amounts of co expressed Renilla luciferase in each sample. The Tat-FLAG domain deletion mutant designations are as in A. Data are representative of three independent experiments.