Sox11's partner proteins and targets in differentiated neurons. Sox11's partner proteins and targets in differentiated neurons. A, Coimmunoprecipitation was performed using E14.5 cortical lysate in which antisera for Sox4 or Sox11 or a control IgG was used to pull down protein complexes before Western blotting for Ngn1 and Brn2. Only Sox11 binds Ngn1; both Sox4 and Sox11 bind Brn2. B, The NeuroD1 locus, with the genomic organization indicated at the top and levels of conservation between mouse and human indicated below by the height of the peaks. The promoter has been magnified in the gray box, with possible Ngn (black), Sox (red), and Brn2 sites indicated. Regions 1–3, studied with ChIP, are indicated by bars at the bottom. C, ChIP using E14.5 cortex and primers specific for proximal (1), middle (2), and distal (3) regions of the NeuroD1 promoter (bars below gray box in B) reveals Sox11 is capable of binding to region 1 but not 2 or 3 of the NeuroD1 promoter. D, E, Transactivation experiments reveal that the NeuroD1 promoter-luciferase construct is not responsive to Sox11 alone, is moderately responsive to Ngn1 alone, and is significantly elevated in the presence of either Sox11 with Ngn1 (D). In contrast, coexpression of Sox11 with Brn2 does not promote NeuroD1 expression (E). F, Transactivation experiments reveal that the Tubb3 promoter-luciferase construct is responsive to Sox11 alone but is suppressed by both Brn2 alone and Brn2 in combination with Sox11. Chao Chen et al. J. Neurosci. 2015;35:10629-10642 ©2015 by Society for Neuroscience