C. Benyajati et al., MULTIPLE ISOFORMS OF GAGA FACTOR, A CRITICAL COMPONENT OF CHROMATIN STRUCTURE, Nucleic acids research, 25(16), 1997, pp. 3345-3353
The GAGA transcription factor of Drosophila melanogaster is ubiquitous
and plays multiple Poles. Characterization of cDNA clones and detecti
on by domain-specific antibodies has revealed that the 70-90 kDa major
GAGA species are encoded by two open reading frames producing GAGA fa
ctor 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 dif
ferent glutamine-rich C-termini, Purified recombinant GAGA-519 and GAG
A-581 proteins can form homomeric complexes that bind specifically to
a single GAGA sequence in vitro, The two GAGA isoforms also function s
imilarly in transient transactivation assays in tissue culture cells a
nd in chromatin remodeling experiments in vitro, Only GAGA-519 protein
accumulates during the first 6 h of embryogenesis. Thereafter, both G
AGA proteins are present in nearly equal amounts throughout developmen
t; in larval salivary gland nuclei they colocalize completely to speci
fic regions along the euchromatic arms of the polytene chromosomes, Co
immunoprecipitation of GAGA-519 and GAGA-581 from crude nuclear extrac
ts and from mixtures of purified recombinant proteins, indicates direc
t interactions, We suggest that homomeric complexes of GAGA-519 may fu
nction during early embryogenesis; both homomeric and heteromeric comp
lexes of GAGA-519 and GAGA-581 may function later.