HAP1 is a member of a family of fungal transcription factors that contain a Zn2Cys6 binuclear cluster domain and bind as homodimers to sequences containing two DNA half sites. We have determined the 2.5 Å crystal structure of HAP1 bound to a cognate upstream activation sequence from the CYC7 gene. The structure reveals that HAP1 is bound in a dramatically asymmetric manner to the DNA target. This asymmetry aligns the Zn2Cys6 domains in a tandem head-to-tail fashion to contact two DNA half sites, positions an N-terminal arm of one of the protein subunits to interact with the inter-half site base pairs in the DNA minor groove, and suggests a mechanism by which DNA-binding facilitates asymmetric dimerization by HAP1. Comparisons with the DNA complexes of the related GAL4, PPR1 and PUT3 proteins illustrate how a conserved protein domain can be reoriented to recognize DNA half sites of different polarities and how homodimeric proteins adopt dramatically asymmetric structures to recognize cognate DNA targets.
CITATION STYLE
King, D. A., Zhang, L., Guarente, L., & Marmorstein, R. (1999). Structure of a HAP1-DNA complex reveals dramatically asymmetric DNA binding by a homodimeric protein. Nature Structural Biology, 6(1), 64–71. https://doi.org/10.1038/4940
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