Program of the 2001 International Worm Meeting - Sternberg Lab ...

533
533. MAB-18 BI-DIRECTIONALLY
REGULATES MALE TAIL
COLLAGEN GENE AND SPERM
SPECIFIC PROTEIN GENE IN
CAENORHABDITIS ELEGANS
Tetsuya Bando, Tatsuji Ikeda,
Hiroaki Kagawa
Graduate School of Natural Science and
Technology, Okayama University, 3-1-1
Tsushima-naka, Okayama 700-8530, JAPAN
Gene-expression controls in tissue, stage and
sex specificities are one of the most interesting
subjects. Bi-directional promoter is defined as
1) two genes are located bi-directionally 2) both
promoters are overlapped each other.
Bi-directional promoter is found in lambda
phage, bacteria, fruit fly, mouse, and human.
None of more than 1,000 candidates in the C.
elegans genome was analyzed. We found
spe-17-like gene (designated spe-TI ) and sqt-3
(col-1) -like gene (designated col-TI ) in the
cosmid clone C46C8 maps in the center of
chromosome V of C. elegans. SPE-TI is a
Ser/Thr rich hydrophilic protein and COL-TI is
a cuticular collagen similar to SQT-3 at the rate
of 84%. Both genes are separated by 1.3 kb and
are transcribed bi-directionally. It is of interest
to know how and which factors control the gene
expression of both. Using the promoter/lacZ
fusion plasmids, we analyzed the promoter
activity of each of genes. spe-TI was expressed
in about 80 cells of spermatheca after 4th larval
stage of hermaphrodite under the control of
0.7kb upstream fragment. col-TI was expressed
only in the male tail tip of adult under the
control of the 0.6kb upstream fragment. These
results suggest that both promoters may overlap
to each other and both genes are regulated by
sex-specific bi-directional promoter.
Transcription factors regulating spe-TI and
col-TI were identified with yeast one-hybrid
screen system by using the promoter specific
regions. After screening approximately 1.4x10 6
yeast transformants for spe-TI and 8.5x10 5
yeast transformants for col-TI , 4 plasmids and 5
plasmids were identified respectively.
Surprisingly, all 9 plasmids came from cDNA of
mab-18 isoform II promoting male tail ray6
formation and are most closely related to the
vertebrate Pax-6. In vertebrate, Pax-6 is used for
eye crystal formation with HMG class
transcription factors but did not use for
533
spermatogenesis nor collagen gene expression.
We also found the Pax-6 homeodomain binding
sequence on 1.0kb upstream of col-TI and 1.1kb
upstream of spe-TI respectively. col-TI::lacZ
was not expressed in mab-18 mutant animals
but heat shock promoter derived ectopic
MAB-18 cannot activate col-TI::gfp expression
ectopically. These results suggest that MAB-18
stimulates col-TI expression directly in tissue or
stage-specifically, but another factor(s) are
necessary for normal col-TI expression. We
believe that bi-directional promoter presented
here is a useful example of understanding the
sex-specific morphological changes in terminal
differentiation.