The glutamine-rich domain of the Drosophila GAGA factor is necessary for amyloid fibre formation in vitro, but not for chromatin remodelling

The Drosophila GAGA factor binds specifically to the sequence GAGAG, and sy nergises with nucleosome remodelling factor to remodel chromatin in vitro. It consists of an N-terminal domain (POZ/BTB) which mediates protein-protei n interactions, a central region which contains the DNA-binding domain, and a C-terminal glutamine-rich region. It is shown that the glutamine-rich re gion is responsible for the formation of fibres in vitro which, on the basi s of their tinctorial properties and CD spectra, may be classified as amylo id fibres. A large structural change, probably resulting in beta-sheet stru cture, is observed upon fibre formation. Mutants containing the central reg ion, either alone or together with the glutamine-rich region, are largely l acking in secondary structure but they bind specifically to the cognate DNA and are able to remodel chromatin in vitro. Consequently, neither the N-te rminal domain nor the C-terminal glutamine-rich regions of the GAGA factor are necessary for chromatin remodelling in vitro. (C) 1999 Academic Press.