Key Residues Characteristic of GATA N-fingers Are Recognized By FOG

Abstract

Protein-protein interactions play significant roles in the control of gene expression. These interactions often occur between small, discrete domains within different transcription factors. In particular, zinc fingers, usually regarded as DNA-binding domains, are now also known to be involved in mediating contacts between proteins. We have investigated the interaction between the erythroid transcription factor GATA-1 and its partner, the 9 zinc finger protein, FOG (Friend Of GATA). We demonstrate that this interaction represents a genuine fingerfinger contact, which is dependent on zinc-coordinating residues within each protein. We map the contact domains to the core of the N-terminal zinc finger of GATA-1 and the 6th zinc finger of FOG. Using a scanning substitution strategy we identify key residues within the GATA-1 N-finger which are required for FOG binding. These residues are conserved in the N-fingers of all GATA proteins known to bind FOG, but are not found in the respective C-fingers. This observation may, therefore, account for the particular specificity of FOG for N-fingers. Interestingly, the key N-finger residues are seen to form a contiguous surface, when mapped onto the structure of the N-finger of GATA-1.Individual eukaryotic transcription factors rarely work alone to activate gene expression. Diverse collections of proteins are typically found assembled at promoters and enhancers, where they are thought to act by recruiting the basal transcriptional machinery and/or by influencing chromatin structure (for review, see Refs. 1-3). Many different types of protein-protein interactions are required for the coordinated formation of an active transcription complex. These interactions can be grouped into 4 main classes: homotypic interactions, such as the dimerization of leucine zippers; short-range interactions, involved in the cooperative binding of factors at adjacent DNA elements; local interactions between DNA-bound proteins and their ancillary factors, such as coactivators or corepressors; and long range interactions between factors bound at widely spaced control elements, which may mediate DNA looping. Although much is now known about transcription factor dimerization and the way in which proteins contact DNA, much less is known about the molecular interactions made between different transcription factors.It is now apparent that some of the well defined structures known to be involved in protein-DNA interactions are also involved in mediating contacts between different proteins. In particular, there are now several examples of zinc finger domains which are involved in protein-protein interactions (4). In some cases, such as GATA fingers (see below), these domains are thought to make both protein-protein (5-9) and protein-DNA contacts (10), whereas in other cases, such as the Cterminal fingers of the Ikaros family proteins, the zinc fingers appear to be exclusively dedicated to protein-protein contacts (11). We have investigated the molecular basis of the interaction between the zinc finger protein...

Protein-Protein Interaction between Fli-1 and GATA-1 Mediates Synergistic Expression of Megakaryocyte-Specific Genes through Cooperative DNA Binding

“…The residues in the tail of the N finger appear to be crucial for its interaction with Fli-1. These residues differ from those required for the interaction with GATA-1's cofactor FOG, which is mediated through the residues within the core of the N finger itself and not the tail (11). Previous studies (12) have suggested that FOG might tether to a number of Ets factors (including Fli-1, Ets-1, and PU.1) to mediate the expression of the GPIIb gene.…”

“…The inserts were digested with EcoRI and SalI and subcloned into the same sites of pGexJT. The GST-mGATA-1 and pRcCMVmGATA-1 constructs used have been described previously (11,23). The GPIX-567 luciferase reporter construct has also been published previously (9).…”

GATA1 Function, a Paradigm for Transcription Factors in Hematopoiesis

“…The 3D structure of A201 to P240 of human and mouse GATA1 is displayed as a ribbon (pink); the zinc atom is displayed as an orange sphere. The positions of the zinc-chelating Cys residues on the ribbon are indicated in yellow; the positions of residues involved in the interaction with FOG-1 are in blue (23). Side chains are shown for the residues mutated in patients.…”

Antagonism between C/EBPβ and FOG in eosinophil lineage commitment of multipotent hematopoietic progenitors

“…The recent finding that the GATA-1 cofactor Friend of GATA (FOG) is required for the development of the thrombocytic lineage at a very early stage (Tsang et al 1998) led us to examine the role of FOG in the generation of MEPs and their differentiation. The FOG protein contains nine zinc fingers, at least two of which are capable of binding to the aminoterminal zinc finger (NF) of GATA-1 (Tsang et al 1997;Fox et al 1998Fox et al , 1999Crispino et al 1999). This interaction is necessary for the ability of GATA-1 to promote terminal erythroid differentiation (Crispino et al 1999), and GATA-1 and FOG cooperate to induce a megakaryocytic phenotype in the 416B myeloid cell line (Tsang et al 1997).…”