title: Structural analysis of MED-1 reveals unexpected diversity in the mechanism of DNA recognition by GATA-type zinc finger domains.
abstract: MED-1 is a member of a group of divergent GATA-type zinc finger proteins recently identified in several species of Caenorhabditis. The med genes are transcriptional regulators that are involved in the specification of the mesoderm and endoderm precursor cells in nematodes. Unlike other GATA-type zinc fingers that recognize the consensus sequence (A/C/T)GATA(A/G), the MED-1 zinc finger (MED1zf) binds the larger and atypical site GTATACT(T/C)(3). We have examined the basis for this unusual DNA specificity using a range of biochemical and biophysical approaches. Most strikingly, we show that although the core of the MED1zf structure is similar to that of GATA-1, the basic tail C-terminal to the zinc finger unexpectedly adopts an alpha-helical structure upon binding DNA. This additional helix appears to contact the major groove of the DNA, making contacts that explain the extended DNA consensus sequence observed for MED1zf. Our data expand the versatility of DNA recognition by GATA-type zinc fingers and perhaps shed new light on the DNA-binding properties of mammalian GATA factors.
authors.affiliation: School of Molecular and Microbial Biosciences, University of Sydney, New South Wales 2006, Australia.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Lowry
authors.forename: Roland
authors.initials: R
authors.lastname: Gamsjaeger
authors.forename: Sock Yue
authors.initials: SY
authors.lastname: Thong
authors.forename: Wendy
authors.initials: W
authors.lastname: Hung
authors.forename: Ann H
authors.initials: AH
authors.lastname: Kwan
authors.forename: Gina
authors.initials: G
authors.lastname: Broitman-Maduro
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Matthews
authors.forename: Morris
authors.initials: M
authors.lastname: Maduro
authors.forename: Joel P
authors.initials: JP
authors.lastname: Mackay
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000378:metabolism*; D002151:Calorimetry; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D024202:Electrophoretic Mobility Shift Assay; D050980:GATA Transcription Factors / Q000737:chemistry* / Q000378:metabolism*; D050982:GATA1 Transcription Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017386:Sequence Homology, Amino Acid; D020349:Surface Plasmon Resonance; D016335:Zinc Fingers
chemical_list: D029742:Caenorhabditis elegans Proteins; D017931:DNA Primers; D050980:GATA Transcription Factors; D050982:GATA1 Transcription Factor; C433251:MED-1 protein, C elegans; D004247:DNA