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. Author manuscript; available in PMC: 2011 May 18.
Published in final edited form as: Nat Commun. 2011 Feb;2:187. doi: 10.1038/ncomms1187

Figure 8. Models for the interaction between DNA-binding transcription factors and Brg1.

Figure 8

Two models for the interaction between DNA-binding transcription factors and Brg1. Model (a) is based on the dosage-sensitive interrelationship between DNA-binding transcription factors (represented by Tbx5) and Brg1. In Brg1 +/− hearts, some Tbx5-binding events are not accompanied by concomitant Brg1 binding, resulting in decreased gene expression. In Tbx5 +/− hearts, Brg1 can only interact with one of two potential Tbx5-binding events, but may still interact more weakly with other DNA-binding transcription factors (X). In Tbx5 +/− ;Brg1 +/− hearts, all quantitative interactions are impaired, leading to further reduction in target gene expression. Model (b) is based on the normalization of gene expression in Tbx5 +/− ;Brg1 +/− and Nkx2-5 +/− ;Brg1 +/− hearts, and is based on the allelic balance between the two genes. In Brg1 +/− hearts, the ratio of Tbx5 to Brg1 alleles is now 2:1, which allows some Tbx5-binding events to interact with other factors, including a hypothetical repressor protein (Y). In Tbx5 +/− hearts, the ratio of Tbx5 to Brg1 alleles is now 1:2, which allows some Brg1-binding events to interact with other factors, including a hypothetical repressor or sequestrating protein (Z). In Tbx5 +/− ;Brg1 +/− hearts, the balance is restored to 1:1, eliminating the potential for other interactions.