Worm Breeder's Gazette 10(1): 70

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Suppressors Involved in Processing of unc-54 mRNA?

R. Pulak and P. Anderson

In the last gazette (vol.9 #3,40-41) we reported on our study of 
spontaneous deletions at the unc-54 locus.  One allele, r293, was of 
particular interest.  The deleted material of r293 extends from 
nucleotide 8217 to 8472 (the base coordinates are from Karn et al.
[PNAS 80:4253(1983)]).  These 256 nucleotides lie 3' to the amino acid 
coding sequence.  The protein coding sequence of unc-54 ends with a 
UAA STOP at coordinates 8176-8178.  The deletion begins 38 bp 
downstream of the STOP codon and spans the putative poly-adenylation 
signal (A2UA3), located at 8344.  Although no amino acid coding 
sequence is missing, the phenotype of a r293 homozygote is that of a 
typical unc-54 mutant paralyzed, non-egglaying hermaphrodite.
The location of the deletion suggested to us that the mutation 
affects some aspect of mRNA processing such as 3' end formation, 
message stability, message transport, etc.  To investigate the events 
occurring in this mutant, we have isolated 38 EMS-induced psuedo-
revertants.  We estimate the frequency of these revertants to be 
5X10+E-5 per animal among the F2.  This relatively high frequency 
likely indicates that the gene(s) involved can be mutated in many 
different ways to give the revertant phenotype, or that more than one 
gene is involved, or both.  Most psuedorevertants contain suppressors 
that are recessive and unlinked to unc-54: 36 of 37 suppressors are 
recessive; 35 of 36 suppressors are unlinked to unc-54; one of the 
revertants is dominant and is closely linked to unc-54.  Our 
suppressors are not sup-3 alleles (sup-3 alleles are semi-dominant 
suppressors of all unc-54 null alleles).  The motility phenotype of 
the psuedo-revertants is nearly wildtype.  Similarily, the phenotype 
of the suppressors (separated from unc-54(r293)) is approximately wild-
type; none appear to be temperature sensitive, but certain suppressors 
may have a slight defect in vulva morphology.  We haven't finished the 
complementation analysis suppressors, but they comprise at least four 
complementation groups.  We are analyzing mRNA from the various 
suppressors and unc-54(r293) in order to identify the RNA process 
being affected.