Figure 1.

Models for combinatorial transcription regulation between two proteins. (a) The co-localization of two DNA-associated proteins DBD1 and DBD2 on the same gene X in the same cell. (b) The exclusion of two DNA-associated proteins DBD1 and DBD2 on the same gene X in the same cell. Both DBD1 and DBD2 can bind to the gene X, but in different cells.