Worm Breeder's Gazette 8(1): 35

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.

Observation on Introns in C. elegans

T. Blumenthal, E. Zucker, K. Denison, J. Spieth

Figure 1

Karn et al.  [PNAS 80, 4253 (1983)] recently published an intron 
boundary consensus sequence which is in need of some revision.  The up-
to-date consensus is shown below, along with the number of cases of 
deviation from the consensus at each position (out of a possible 14).  
The all-organism consensus is included for comparison [Breathnach and 
Chambon, Ann.  Rev.  Biochem., 50, 349 (1981)].
[See Figure 1]
In C.  elegans, the myosin, collagen, actin, and yolk protein gene 
families all provide examples of genes which contain an intron not 
present in one or more related genes.  In previously analyzed cases it 
has not been possible to determine whether the intron is a late 
arrival into one of the genes or, alternatively, has been lost from 
the other.  However, in one case an interesting aspect of the sequence 
leads us to the belief that a 49-base intron present in yp5 but not 
yp2 has been lost from the latter gene.  The sequence indicates that 
the intron has been removed without alteration of the length of the 
surrounding coding regions.  While the coding regions of yp5 and yp2 
are about 70% homologous over most of their length, the regions around 
the intron are only 43% homologous.  Interestingly, yp2 has apparently 
replaced the portions of the two exons surrounding the intron with a 
duplication of a region found in both genes about 30 bp 3' of the 
intron site.  In this region, 18 out of 24 bp are homologous between 
the two apparently duplicated parts of yp2.
[See Figure 1]
Apparently, a duplication event resulted in formation of a larger 
exon from two smaller ones during the evolution of yp2.  Mispairing 
and gene conversion may have been responsible for loss of this intron.

Figure 1