[
Worm Breeder's Gazette,
1988]
Transposable elements, like Tc1, have a much wider phylogenetic distribution than previously thought. Tc1 and TCb1 (also known as Barney) share sequence identity with the open reading frame (ORF) of the HB elements found in Drosophila melanogaster. The ORFs of Tc1 and Barney can be aligned with HB1 after the introduction of 3 centrally located deletions in HB1. These reading frames would code for proteins with 30% amino acid identity (42% when conservative changes are included). Tc1, Barney and HB1 contain highly conserved blocks of amino acids which are likely to be in the functional domains of the putative transposase. It is unfortunate that the HB elements in Drosophila are defective and can't reveal secrets of mobility. Within the class of inverted repeat elements, a subclass of closely related elements exists. This subclass includes Tc1 and Barney in the Nematoda and HB in Arthropoda. Since these phyla are evolutionarily quite distant it is reasonable to suppose that Tc1-like elements will have a wide distribution within the eukaryotes. Their presence in these two phyla could have resulted from the existence of the element in a common ancestor prior to the time of divergence (>500 million years) or might have resulted from more recent horizontal transfer. The sequence comparisons of Tc1, Barney and HB1 are to be published in Nucleic Acids Research.
[
Worm Breeder's Gazette,
1986]
A repetitive element which is homologous to the transposable element Tc1 from C. elegans resides in C. briggsae. When an EcoRV-cut Tc1 probe is hybridized with moderate stringency to C. briggsae EcoRI- digested genomic DNA, numerous bands can be visualized at a weaker signal than those seen in C. elegans. This Tc1 probe was used to screen a C. briggsae var. G16 Charon 4 library (constructed by T. Snutch). A single EcoRI fragment in each of 13 phage contained Tc1 homology and these have been subcloned. These plasmids are being compared with respect to their restriction map and homologous regions. The restriction sites found in Tc1 are not present in these subclones. The Tc1 homology appears to extend over the entirety of the Tc1 element. The size of the C. briggsae repetitive element is not known. A SalI/EcoRI fragment with Tc1 homology from one of the C. briggsae plasmids was hybridized against DNA from two C. briggsae strains, G16 and Zuckerman. The repetitive element is at low copy number ( approximately fifteen bands in G16) in both strains, but there are at least six banding differences between these strains. The repetitive element has been named Barney.