Worm Breeder's Gazette 11(4): 68

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.

unc-116 Shares Sequence Homology with the C-Terminal Domain of the Drosophila Kinesin Heavy Chain

Neela Patel and Jorge R. Mancillas

Unc-116 is a genetic locus identified by spontaneous mutation during 
a screen of TR679 for genes involved in axonal guidance.  Unc-116(
e2312) hermaphrodites display abnormal locomotion, primarily during 
backward movement.  Anatomical abnormalities include the misplacement 
of axons which normally occupy a lateral position and abnormal hyp-7 
nuclear migrations along the circumferential axis (Thierry-Mieg and 
Mancillas, in preparation).
Unc-116 was cloned by a combination of transposon tagging and 
location in the physical map, and partial cDNAs were isolated from the 
Ahringer library using genomic probes.  We have obtained sequence 
information from those cDNAs as well as genomic fragments.  Comparison 
of sequences available in Genbank to sequence determined from the end 
of a 1.4 kb cDNA revealed a 63% identity to Drosophila melanogaster 
heavy chain kinesin (Yang et al, Cell (1989) 56: 879-889), over a 
stretch of 307 nucleotides.  At the amino acid level, using the best 
open reading frame from the unc-116 sequence, unc-116 is 57% identical 
(71% similar) to amino acids 855-975 in the c-terminal end of 
Drosophila kinesin.  The similarity to unc-116 is within the 
structural domain of kinesin which Yang et. al. propose to be involved 
in interactions with vesicles, organelles, or the light chain of 
kinesin and does not include any of the postulated ATP and microtubule 
binding domains.  When the nucleotide sequence and predicted amino 
acid sequence of unc-116 were compared to Genbank and 
NBRF/Swissprotein data bases, respectively, no other significant 
matches were found.  Sequence data (approximately 300 bp) of the other 
end of the 1.4 kb clone, 650 nucleotides away from the kinesin-like 
domain, showed no significant matches to Genbank or NBRF/Swissprotein 
data base entries.  We suggest that unc-116 has a domain similar to 
the c-terminal 'tail' domain of Drosophila kinesin, and that this 
domain may play a role in 'recognition' events for both axonal 
guidance and intracellular transport.  We are currently sequencing the 
remainder of the 1.4 kb cDNA and have used it as a probe to obtain 
longer, putative full-length clones from Stuart Kim's gt19 mixed stage 
hermaphrodite library.  We obtained 150 positives after screening 100,
000 plaques, a frequency higher than anticipated (approx.  1/670).  We 
plan to sequence our longer clones as well.
We have also started to characterize the phenotype and mating 
efficiency of unc-116 males.  From preliminary observations, unc-116 
males display abnormal backward locomotion, adopting a U-shape when 
stimulated by a tap on the head.  The posterior third of the animals 
appears abnormal: rigid, slightly swollen, and clear.  Those 
morphological abnormalities are likely to be responsible for the low 
mating efficiency we have observed.