FIG. 1.

Tbx5 protein NLS sequences. (A) Schematic representation of the chicken Tbx5 protein (GenBank/EBI Data Bank number NP_989504) with the N-terminal DNA-binding domain and the C-terminal transactivation domain. The two NLS sequences are indicated and consist of amino acids 78 to 90 in the DNA-binding domain (NLS1) and amino acids 325 to 340 in the transactivation domain (NLS2). (B) Subcellular localization of Tbx5 NLS mutants. COS-7 cells were transfected with expression vectors encoding the indicated EGFP-Tbx5 fusion proteins. After transient expression, cells were fixed and imaged using a Zeiss 510 Meta scanning confocal microscope with a Plan Apochromat 63× objective/1.4 numerical aperture oil differential interference contrast lens. Tbx5 is detected in the nuclei of transfected cells, whereas all three of the Tbx5 NLS mutant forms reveal robust distribution of the protein in the cytoplasm as well as in the nuclei. White scale bar = 20 μm.