Worm Breeder's Gazette 11(1): 26
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.
We have previously reported the isolation and characterization of a cDNA clone corresponding to the 4.6 Kb transcript of tra-2 (1). Primer extension and S1 protection analyses of the 5' end strongly suggested that this tra-2 transcript was trans-spliced. Sequence ambiguities impeded identification of the leader by dideoxy sequencing RNA using reverse transcriptase. Consequently, we have used a PCR method (2) to obtain additional cDNA clones that encompass the entire 5' end of the 4.6Kb transcript. In brief, the 4.6Kb transcript of tra- 2 is trans-spliced to the SL-2 sequence originally found associated with the C. elegans gene, GAPDH (3). Surprisingly, we have also isolated 5 other cDNA clones that contain variations in the SL-2 sequence. These differences include insertions and deletions that result in a 23 or 21 nucleotide leader, and base substitutions in the original SL-2 sequence. We do not know if these differences are artifacts induced during the PCR reaction or if they reflect heterogeneity among SL-2 genes. If the latter, then this observed heterogeneity could explain our inability to identify the tra-2 leader by reverse transcriptase sequencing. These results also imply that a transcript can be trans-spliced to leader sequences encoded by different genes, perhaps with different regulatory functions.