INVOLVEMENT OF THE N-FINGER IN THE SELF-ASSOCIATION OF GATA-1

Zinc fingers are recognized as small protein domains that bind to spec ific DNA sequences. Recently however, zinc fingers from a number of pr oteins, in particular the GATA family of transcription factors, have a lso been implicated in specific protein-protein interactions. The eryt hroid protein GATA-1 contains two zinc fingers: the C-finger, which is sufficient for sequence-specific DNA-binding, and the N-finger, which appears both to modulate DNA-binding and to interact with other trans cription factors. We have expressed and purified the N-finger domain a nd investigated its involvement in the self-association of GATA-1. We demonstrate that this domain does not homodimerize but instead makes i ntermolecular contacts with the C-finger, suggesting that GATA dimers are maintained by reciprocal N-finger-C-finger contacts. Deletion anal ysis identifies a 25-residue region, C-terminal to the core N-finger d omain, that is sufficient for interaction with intact GATA-1. A simila r subdomain exists C-terminal to the C-finger, and we show that self-a ssociation is substantially reduced when both subdomains are disrupted by mutation. Moreover, mutations that impair GATA-1 self-association also interfere with its ability to activate transcription in transfect ion studies.