FIGURE 1:

Syntaxin 16 is required for cytokinesis. HeLa cells were incubated with adenovirus designed to express the indicated Sx-ΔTM construct at identical multiplicity of infection (in the experiment shown, 30:1), empty virus or not infected (control), as described in Materials and Methods. At 48 h later, cells were fixed and stained with anti-tubulin antibodies and DAPI and the frequency of binucleate cells counted. (A) Quantification of five independent experiments of this type. Sx6-ΔTM and Sx16-ΔTM significantly increased the frequency of binucleate cells (*p < 0.05), using at least three different batches of virus. (B) Typical fields of cells infected with Sx12-ΔTM or Sx16-ΔTM as indicated and stained for tubulin (red; tubulin), Sx16 (green; Sx16) or DNA (blue; DAPI). Note that for Sx16-ΔTM–infected cells, the high level of overexpression of Sx16-ΔTM required the use of reduced gain/laser power during collection of the image. (C) Comparison of the frequency of binucleate cells in cells infected with empty virus, Sx16-ΔTM, or Sx16-full length. (D) HeLa cells were transfected with an siRNA SmartPool designed to knock down Sx16 or a scrambled siRNA SmartPool control and then incubated for 48 h after transfection before fixation and staining with anti-Sx16. Data from a typical experiment. Left, typical cell in telophase, with endogenous Sx16 present near the midbody. See Figure 3 for Sx16 protein levels after knockdown. C and D are representative of three or more experiments of this type.