Fig. 4

The Tbx2 Spacer 1 and T-box domains are sufficient for R-Smad association. a-e Smad1 physically associates with Tbx2 via the T-box. Embryos were injected at the two-cell stage with 1 ng of RNA synthesized from the indicated deletion construct. Pull-down of native Smad1 from injected embryos leads to co-immunoprecipitation of the exogenous deletion construct. Normal rabbit IgG antibodies were used in parallel studies as a negative control. f-j Smad2 physically associates with Tbx2 via the T-box. Embryos were injected at the two-cell stage with 1 ng of RNA synthesized from the indicated deletion construct and flag-smad2. Pull-down of Flag-Smad2 from injected embryos leads to co-immunoprecipitation of the exogenous deletion construct. Normal rabbit IgG antibodies were used in parallel studies as a negative control