Worm Breeder's Gazette 10(3): 40

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.

More unc-5 Sequence

C. Leung-Hagesteijn, J. Culotti, B. Stern, E. Hedgecock and A. Spence

Figure 1

unc-5 is required to guide certain migrating axons and mesodermal 
cells dorsalward on the nematode epidermis (1987 CSH Meeting Abstracts,
p.73).  We have sequenced approximately 1500 base pairs of unc-5 open 
reading frame comprising four putative exons and spanning 4.5 KB of 
the genome (see map below).  The direction of transcription is right 
to left on the genetic map.  The unc-5 message appears to be 
approximately 3 KB as determined by probing Northern blots with 
various subcloned fragments from the unc-5 region, so there is clearly 
more sequencing to be done.  As reported in WBG vol.10#2 p. 118, one 
putative unc-5 exon encodes a pair of tandemly arranged domains (WSX 
domains) found in a variety of unrelated proteins that exhibit cell 
and basement membrane binding properties.  The homology with these 
proteins does not extend beyond this domain, nor have we found 
significant homology with any other proteins in the NBRF database.  
The sequence determined thus far does have a couple of interesting 
features.  For example, there is a possible transmembrane domain of 26 
uncharged amino acids just 3' to the WSX domains.  This situation 
parallels that observed in the circumsporozite protein of the malarial 
parasites in which the WSX domain is adjacent to a transmembrane 
domain (1-3); however, it is too soon to say whether unc-5 encodes a 
transmembrane protein, particularly since we have yet to identify an 
initiation codon or putative signal sequence.
Another intriguing feature of the unc-5 sequence is that intron C (
map) contains a direct repeat of 20 base pairs (TTTCAAAAATTTCATAAAAT 
on the coding strand).  We don't know what, if any, function this 
sequence might have, but if any of you have any ideas we would be 
interested to hear them.
[See Figure 1]

Figure 1