Worm Breeder's Gazette 11(4): 42

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-22 Update

Guy Benian, Mary Morris, Kate Tobin and Steve L'Hernault

Figure 1

We can finally report the 5' end of the unc-22 message and the N-
terminus of twitchin.  We sequenced an additional 7825 bps to the 
right of our previous sequence and now have a total of 54,963 bp of 
genomic sequence.  Previously, we believed that a likely initiator 
methionine for twitchin resided at 21,952, but this is located 12,914 
bp downstream of the Tc1 insertion site for the unc-22 allele st139.  
Computer inspection for likely coding sequence and motifs I and II 
were not successful.  During a search for cDNA clones for spe-17, one 
clone, pSL12, turned-out to hybridize only to the unc-22 message and 
its sequence is distributed between position 3958 and 9439.  The 
remaining gap in coding sequence was filled by PCR of first strand 
cDNA using one primer for coding sequence just 3' of the previous ATG 
and one primer in coding sequence defined by pSL12.  The 5' end of the 
message was determined by primer extension and by virtue of being 
trans-spliced to SL1 RNA (indicated by PCR with first strand cDNA and 
SL1 primer, and because pSL12 begins with the last 9 bp of SL1).  
Including a 5' untranslated sequence of 149 bp, we need to tack-on an 
additional 2522 bp of message, yielding a final unc-22 message of 21,
614 bp!  This additional coding sequence is interrupted by 17 introns, 
the largest being 7402 bp (final total of 30 introns) and 17 new exons 
each no longer than 370 bp, the smallest being 54 bp.  Most 
importantly, this adds 791 amino acids (total of 6840) to twitchin 
resulting in a single polypeptide of 753,570 Da.  There are 4 
additional copies of motif II (total of 30) and 2 segments of 167 
amino acids and 189 amino acids having no homologies to proteins in 
the databases.  The Tc1 insertion site for st139 resides in coding 
sequence for the third copy of motif II, 7 bp downstream of the 7th 
intron.  In the following figure motif I copies are denoted 1-31 and 
motif II copies are denoted 1'-30'.
[See Figure 

Figure 1