For immunofluorescence analysis, MCF-7 cells were fixed and permeabilized using ice cold 100% Acetone for detection of endogenous CDK9 using Anti-CDK9 Recombinant Rabbit Monoclonal Antibody (Product # 703704, 1:100 dilution) and labeled with Goat anti-Rabbit IgG (H+L) Superclonal™ Secondary Antibody, Alexa Fluor® 488 conjugate (Product # 703404, 1:2000). Panel a) shows representative cells that were stained for detection and localization of CDK9 protein (green), Panel b) is stained for nuclei (blue) using ProLong™ Diamond Antifade Mountant with DAPI (Product # P36962). Panel c) represents cytoskeletal F-actin staining using Rhodamine Phalloidin (Product # R415, 1:300). Panel d) is a composite image of Panels a, b and c clearly demonstrating nucleus and cytoplasmic localization of CDK9. Panel e) represents control cells with no primary antibody to assess background. The images were captured at 60X magnification.