β-actin monomers incorporate into filaments at cell contacts in MDCK cells in a 3′ UTR–dependent manner. (A) De-convolved single plane epifluorescence image of MDCK cells expressing full-length β-actin GFP (green) at steady state (SS), in 1 h low Ca2+ (LC), or 3 h post-Ca2+ switch experiment (Rec 180). F-actin was stained by Alexa350 (blue) and E-cadherin using Cy3 (red). (B) De-convolved single plane epifluorescence image of MDCK cells expressing Δ3′ UTR β-actin (green) at steady state (SS), in 1 h low Ca2+ (LC), or 3 h post-Ca2+ switch experiment (Rec 180). F-actin was stained by Alexa350 (blue) and E-cadherin using Cy3 (red). Arrows indicate the places where puncta of β-actin GFP are incorporated into filaments along the contact. Note asterisks, which indicate holes in the monolayer. Scale bars, 20 μm.
