Worm Breeder's Gazette 15(2): 52 (February 1, 1998)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

A second look at the dpy-20 encoded protein, a novel transcription factor.

M. Yusuf Ali, Omar S. Siddiqui, Shahid S.Siddiqui

Lab. of Molecular Biology, Toyohashi University of Technology, Tempaku-cho, Toyohashi 441, Japan.

Previously it has been shown that when the  wild type dpy-20 gene  is
overexpressed ectopically in transgenic animals, it suppresses 
transcrption of the alpha-1 and alpha-2 tubulin genes in the ventral
cord motor neurons very significantly, with little or no effect in the
head and tail of the animals (Fukushige and Siddiqui,Transgenic Res.4;
332-340,1995).The dpy-20 IV encodes a non collagen novel protein of 359
amino acid  with no significant similarity to any protein in various 
data bases (Clark et al.1995). We hypothesized that the dpy-20 gene may
affect the transcription in  ventral cord motor neurons not only of the
alpha  tubulin genes but perhaps  also of other genes that are specific
to motor neurons. We have previously shown that the dpy-20 gene
interacts with unc-104, unc-116 and osm-3 genes that encode different
kinesin motor proteins in C. elegans (C. elegans International
Meeting, 1997).  To test the notion whether the  dpy-20 is a specific
regulator of transcription in the ventral cord motor neurons, we have
constructed a  variety of  double mutants using the  dpy-20(e2017) amber
allele (Hodgkin, 1985), with different  uncoordinated mutants  (Brenner,
1974),  known to be affected in the ventral cord motor neuron
development, such as the  unc-4(e120) (White et al 1992; Miller et al.,
1992), unc-5(e53) (Siddiqui, 1990; Hedgecock et al,1990;
Leung-Hagesteijn et al,1992; Hamelin et al.1993), unc-13(e51) (Brenner
1974; Ahmed et al 1992; Nguyen et al. 1995), unc-104(rh1016,rh1017) 
(Otsuka et al.,1991) , unc-25(e156) (Thomas 1990;McIntire et al. 1993;
Reiner and Thomas 1995), unc-51(e369) (Hedgecock et al. 1985; McIntire
et al. 1992; Ogura et al.1994), unc-55(e402)  (Walthall and Plunkett
1995), unc-70(e524)(Park and Horvitz 1986a; Johnsen and Baillie 1991),
unc-86(e1416) (Chalfie et al. 1981; Finney et al.1988; Baumeister et
al. 1996), and unc-32(e189)( Brenner 1974; Nguyen et al. 1995) etc.
Interestingly, all of these double mutants are severely affected in
growth and show great reduction in brood size. These double mutants are
clearly slow to grow, mostly sterile, severely uncoordinated, and often
die as bag of worms with only one or two progeny. In controls, the
double mutants between the dpy-20(e2017) and muscle specific mutants,
such as the unc-68(e540) Brenner 1974; Lewis et al. 1980), unc-54(e190) 
(Epstein et al; McLachlan and Karn 1982;Dibb et al. 1989; Bejsovec and
Anderson 1990) unc-15(e73) (Kagawa 1989; Gengyo-Ando and Kagawa 1991;
Epstein et al. 1993) were constructed and tested for their viability and
brood size. No significant reduction in the brood size was observed.  
These observations suggest a role of dpy-20 gene in regulating the
expression of genes that are expressed in the ventral cord motor

The hypothesis that the dpy-20 gene regulates gene expression in ventral
cord motor neurons got further support when we showed that a reporter
gene dpy-20::lacZ, expresses in the set of ventral cord motor neurons
and hypodermal cells (M. Y. Ali, Z. K. Siddiqui, Diana Janke, David
Baillie, and Shahid Siddiqui, unpublished, see the accompanying abstract
in this issue of WBG).  Genetic data obtained from the double mutants is
consistent with the observation that the dpy-20 gene is expressed in the
ventral cord motor neurons. Based on these observations we have
re-examined the protein sequence of DPY-20 and looked for its identity
both from computer homology search and visual inspection. To our
surprise (and delight) we found that indeed the DPY-20 shares
significant homology in 18 small regions with a variety of transcription
factors and regulatory proteins conserved across different species from
the yeast to humans. For example, it shows homology with Drosophila
ecdysone inducible protein(E75A,E75B) (Segraves WA and Hogness DS,1990), 
liver specific transcription factor, human(HNFA) (Bach I,1990), 
homeobox protein DLX-2 (HMD2, human) (Selski D.J, 1993), zinc finger
protein, (HRX,mouse)(MA Q,et al.,1993), insulin receptor
substrate(IRS1,human) (Nishiyama M, et al.,1992), zinc finger protein
(MGF3,mouse) (Passananti C, et al.,1989), renal transcription factor
KID-1(rat) (Witzgall R, et al.1993), human basic transcription factor
BTF2 (Fischer L,et al.,1992), transcription factor GAGA, Drosophila
(Soeller W.C. et al.,1993) and  C. elegans homeobox protein lin-39
(Clark SG et al.,1993) etc. Dpy-20 protein shares  significant
homology(62%) with a small region(19 aa) of Lin -39. The overall 
structural similarity between the Dpy-20 and Lin-39 is 41%. We propose
that the Dpy-20 may  be a Lin-39 like  transcription factor.

It is also possible that dpy-20 is different from all other known 
transcription factors and defines  a novel transcription factor.
Interestingly, the dpy-20 genomic sequence contains different DNA
binding sequences that are known to bind various transcription factors
such as the NK-2 , POU factor and IRF factors etc. Currently, we are
doing gel mobility shift assays to test the DNA/protein interaction with
respect to examine the interaction of the Dpy-20 protein and different
genomic sequences, and also the binding of various factors to the dpy-20
genomic sequences. Whether the Dpy-20 is regulating expression of
various genes in the ventral cord motor neurons directly or perhaps
controlling the transcription of other regulatory gene(s) remains to be

We thank David Baillie, Ken Nishikawa, Johji Miwa, Tony Otsuka, Y.
Kohara, T. Motohashi, A. Fire, Ian Hope, R. Hosono, K. Harada, for their
help and cooperation and T.Stiernagle for mutant strains.