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Molecular and Cellular Biology, December 2001, p. 8565-8574, Vol. 21, No. 24
Dept. of Molecular Biology, Princeton
University, Princeton, New Jersey 08544
Received 6 July 2001/Returned for modification 14 August
2001/Accepted 4 September 2001
The Drosophila melanogaster GAGA factor (encoded by
the Trithorax-like [Trl] gene) is
required for correct chromatin architecture at diverse chromosomal
sites. The Trl gene encodes two alternatively spliced
isoforms of the GAGA factor (GAGA-519 and GAGA-581) that are identical
except for the length and sequence of the C-terminal glutamine-rich (Q)
domain. In vitro and tissue culture experiments failed to find any
functional difference between the two isoforms. We made a set of
transgenes that constitutively express cDNAs coding for either of the
isoforms with the goal of elucidating their roles in vivo. Phenotypic
analysis of the transgenes in Trl mutant background led
us to the conclusion that GAGA-519 and GAGA-581 perform different,
albeit largely overlapping, functions. We also expressed a fusion
protein with LacZ disrupting the Q domain of GAGA-519. This LacZ fusion
protein compensated for the loss of wild-type GAGA factor to a
surprisingly large extent. This suggests that the Q domain either is
not required for the essential functions performed by the GAGA protein
or is exclusively used for tetramer formation. These results are
inconsistent with a major role of the Q domain in chromatin remodeling
or transcriptional activation. We also found that GAGA-LacZ was able to
associate with sites not normally occupied by the GAGA factor, pointing to a role of the Q domain in binding site choice in vivo.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.24.8565-8574.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
GAGA Factor Isoforms Have Distinct but Overlapping
Functions In Vivo
and
*
Corresponding author. Mailing address: Dept. of
Molecular Biology, Princeton University, Princeton, NJ 08544. Phone:
(609) 258-4979. Fax: (609) 258-1028. E-mail:
pschedl{at}molbio.princeton.edu.
Present address: Dept. of Ecology and Evolution, University of
Chicago, Chicago, IL 60637.
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