Multiple isoforms of GAGA factor, a critical component of chromatin structure.

Nucleic Acids Res 1997 Aug 15;25(16):3345-53

Benyajati C, Mueller L, Xu N, Pappano M, Gao J, Mosammaparast M, Conklin D, Granok H, Craig C, Elgin S

Department of Biology, University of Rochester, Rochester, NY 14627, USA.

The GAGA transcription factor of Drosophila melanogaster is ubiquitous and plays multiple roles. Characterization of cDNA clones and detection by domain- specific antibodies has revealed that the 70-90 kDa major GAGA species are encoded by two open reading frames producing GAGA factor proteins of 519 amino acids (GAGA-519) and 581 amino acids (GAGA-581), which share a common N-terminal region that is linked to two different glutamine-rich C-termini. Purified recombinant GAGA-519 and GAGA-581 proteins can form homomeric complexes that bind specifically to a single GAGA sequence in vitro. The two GAGA isoforms also function similarly in transient transactivation assays in tissue culture cells and in chromatin remodeling experiments in vitro . Only GAGA-519 protein accumulates during the first 6 h of embryogenesis. Thereafter, both GAGA proteins are present in nearly equal amounts throughout development; in larval salivary gland nuclei they colocalize completely to specific regions along the euchromatic arms of the polytene chromosomes. Coimmunoprecipitation of GAGA-519 and GAGA-581 from crude nuclear extracts and from mixtures of purified recombinant proteins, indicates direct interactions. We suggest that homomeric complexes of GAGA-519 may function during early embryogenesis; both homomeric and heteromeric complexes of GAGA-519 and GAGA-581 may function later.

PMID: 9241251, UI: 97388557

Colocalization of GAGA-519 and GAGA-581 along polytene chromosomes.
(a), (b) (c) Fluorescent micrographs of a single set of polytene chromosomes costained with affinity-purified anti-GAGABTB-ZF-C-ter 519 (green) and anti-GAGAC-ter 581 (red) antibodies. (c) Double exposure (merged) showing regions of overlap (yellow). Note the absence of chromocenter staining (upper right).