Lowry JA et al. (2009) J Biol Chem "Structural analysis of MED-1 reveals unexpected diversity in the mechanism of DNA recognition by GATA-type zinc finger domains."

Hung W, Maduro M, Kwan AH, Mackay JP, Broitman-Maduro G, Matthews JM, Thong SY, Gamsjaeger R, Lowry JA

[J Biol Chem, 2009]

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.

Nicholas HR et al. (2008) J Mol Biol "The Caenorhabditis elegans protein CTBP-1 defines a new group of THAP domain-containing CtBP corepressors."

Wu T, Lowry JA, Crossley M, Nicholas HR

[J Mol Biol, 2008]

The C-terminal binding proteins (CtBPs) play roles in diverse cellular processes including transcriptional regulation, Golgi membrane fission, and synaptic ribbon formation. In the context of transcriptional regulation, they function as corepressors, interacting with promoter-bound transcription factors and recruiting a large protein complex that contains chromatin-modifying enzymes. We recently described the structure of a Thanatos-associated protein (THAP) domain that is found in a new member of the CtBP family, the Caenorhabditis elegans CTBP-1 protein. We have identified additional THAP domain-containing CtBPs in the nematode, echinoderm, and cephalochordate lineages. The distribution of these lineages within the animal kingdom suggests that the ancestral form of the animal CtBPs may have contained a THAP domain that was subsequently lost in the vertebrate and arthropod lineages. We also provide functional data indicating that CTBP-1 represses gene expression and homodimerizes and interacts with PXDLS-containing partner proteins, three key features of the previously characterized animal CtBPs. CTBP-1 is therefore the founding member of a new subgroup within the CtBP corepressor family, the THAP domain-containing CtBPs.