Biology Reference
In-Depth Information
peripheral clock is required for normal eclosion in addition to the central
pacemaker in the brain (
Myers, 2003; Myers et al., 2003
). Taken together,
these data support the idea of a direct role for timeless and period in the
regulation of ecdysone synthesis.
11.6. HLH54F (HLH54F)
Drosophila HLH54F
has roles in muscle development and encodes a basic
helix-loop-helix transcription factor that is highly conserved between flies
and vertebrates (
Ismat et al., 2010; Robb, Hartley, Wang, Harvey, & Begley,
1998
).
HLH54F
is also expressed in prothoracic glands of wandering
Bombyx
larvae and
Drosophila
embryos, but its expression in the post-
embryonic stages of
Drosophila
development has not been reported
(
Namiki et al., 2009
). The expression in prothoracic glands could indicate
a role in ecdysteroid biosynthesis or the development of the gland, but we
have to await genetic data before more can be said about the roles of this
transcription factor.
11.7. Ttk (tramtrack)
The
Drosophila tramtrack
gene encodes two protein isoforms, Ttk69 and
Ttk88, which are transcription factors that share an N-terminal BTB/
POZ domain for protein-protein interaction but have different sets of zinc
fingers for distinct DNA-binding specificities (
Giesen et al., 1997; Read &
Manley, 1992; Zollman et al., 1994
).
ttk
is strongly expressed during mid-
embryogenesis and is present in various larval tissues during postembryonic
development. Based on enhancer traps,
ttk
expression was detected in the
prothoracic gland at all three larval stages (
Harvie et al., 1998
). However,
it remains unknown whether
ttk
is important for any aspect of prothoracic
gland development and/or function. It was shown that Ttk69 represses gene
expression mediated by the GAGA factor through attenuating the interac-
tion between GAGA and the general transcription machinery (
Pagans,
Pineyro, Kosoy, Bernues, & Azorin, 2004
). More recent evidence suggested
that the GAGA/Hsf/Ttk69 complex acts downstream of Trunk/Torso sig-
naling in regulating gene expression via remodeling local chromatin struc-
ture (
Chen, Lin, Chen, Chiang, & Liaw, 2009
), raising the interesting
possibility that
ttk
may function as a target of the PTTH/Torso in the pro-
thoracic gland as well. It is interesting to note that Ttk and Broad share the
same type of protein-protein interaction domain (BTB/POZ domains).
Another protein harboring this domain, Batman (a.k.a. Lola like) was
