This is a short list of some of my favourite unusual gene structures in C. elegans. Some of these still pose problems for WormBase curators trying to model their structure and final protein products accurately.
Please add your own favourites!
Exons on opposite strands
eri-6 and eri-7 produce separate pre-messenger RNAs (pre-mRNAs)are trans-spliced to form a functional mRNA, eri-6/7
Two genes one locus
The cha-1 (ZC416.8b) and unc-17 (ZC416.8a) transcripts appear to be derived by alternative splicing of a common precursor. The two genes use a common 5’ untranslated exon; the remainder of the unc-17 gene is nested within the long first intron of cha-1.
ubl-1 - Polyubiquitin
Ubiquitin is a 76-amino-acid protein that has been highly conserved in the evolution of eucaryotes.
Ubiquitin is transcribed as a polycistronic mRNA from this locus, translated into a polyprotein, and then cleaved proteolytically to yield free ubiquitin monomer.
unc-49 encodes Multiple Subunits of a Heteromultimeric GABA Receptor
unc-49 contains a single copy of a GABA receptor N terminus, followed by three tandem copies of a GABA receptor C terminus. Using a single promoter, unc-49 generates three distinct GABA-A receptor-like subunits by splicing the N terminus to each of the three C-terminal repeats.
Non-canonical splice sites
There are many cases of non-canonical splice sites in c. elegans genes.
This is just a well-characterised example.
The donor splice site of intron 7 of F01G12.5b starts with GC instead of GT.
A review of non-canonical splice sites can be found in:
The biggest gene - titin
There is nothing particularly extraordinary about the gene ttn-1, except that it is large.
Examples of RNA editing in C. elegans are hard to come by apart from the targets of RNA editing by adr-1 and adr-2 in nervous tissue (and possibly vulval tissue). The known targets of adr-1 and adr-2 are: ZC239.6, Y6D11A.1, F56A8.7a, W03D8.2 and C54D1.5
There also appears to be C-to-U RNA editing in gld-2
There is a good example of a programmed frameshift in most metazoons: antizyme or ornithine carboxylase: odc-1
There is one selenoprotein in C.elegans: trxr-1