Worm Breeder's Gazette 10(3): 74
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.
At the 1987 CSH worm meeting we reported that using Tc1 as a probe in Northern blot analysis, we observed a polyadenylated transcript in Bergerac but not in Bristol worms. (This was confirmed by Radice, et. al., (WBG 10.2)). These results have been extended and some conclusions can now be drawn: (1) The transcript (approximately 1,500 bases long) is found consistently only in strains that are active in Tc1 transposition. Controls have been done with overexposure of Northern blots of Bristol mRNA; blots were checked with an actin probe for quality and amount of RNA in the preps. We feel sure that we are not just observing the result of a copy number difference of Tc1; the Tc1 homologous transcript is absent in Bristol. The correlation between presence of the transcript and transpositional activity suggests that the secret of regulation of Tc1 activity is in Tc1 transcription regulation. To determine the structure of the transcript, we made a cDNA library of RW7000 and selected Tc1 homologous clones. Twenty were found and these are currently being analyzed. (2) The assumption that Tc1 transcription is essential for transposition is supported by the following: It was previously reported by Carol Trent and Jonathan Hodgkin that a direct descendent of the sma-1 mutant CB30(e30) (which is derived from Bristol N2) had become active in transposition (abstract book 1987 CSH meeting). The active derivative was renamed CB4000. We looked at RNA of CB4000 and it contains a transcript of the same size as Bergerac, which is absent in the N2 strain. This shows that the acquisition of transpositional activity is accompanied by the appearance of this transcript. (3) Somatic excision apparently is independent of Tc1 transcription, because the Bristol strain contains no Tc1 homologous transcripts in somatic cells and still it shows somatic excision of Tc1. If indeed Tc1 transcription is essential for germ-line transposition and excision of Tc1, then somatic excision of Tc1 must be a process that differs significantly from the germ-line events. (4) If the essence of the Bristol/Bergerac difference is in Tc1 transcription, then the next question is what causes the difference in TcA expression. This is the question that we are currently trying to answer.