| Satellite 2 is a 330 base pair repetitive element in the newt, Notophthalmus viridescens (Family: Salamandridae). This element is unusual in that tandemly repeated blocks of satellite 2 are dispersed throughout each of the newt's 11 chromosomes, and transcripts homologous to satellite 2 are present in all newt tissues that have been examined. A function for these transcripts has not yet been found, and it is possible that they are involved solely in the propagation and evolution of this unusual element. Other properties of satellite 2, including its ability to promote transcription and the ability of synthetic satellite 2 transcripts to catalyze their own site-specific cleavage, may also be involved in the mechanism of satellite 2 propagation. We have extensively studied these properties with the idea that a complete description of the molecular biology of satellite 2 will help elucidate its mode of evolution. To complement these studies, we initiated a phylogenetic analysis of satellite 2. Satellite 2 elements were cloned from representatives of three additional salamander families: Ambystoma talpoideum (Ambystomatidae), Amphiuma tridactylum (Amphiumidae), and Eurycea longicauda (Plethodontidae). Despite considerable divergence between the sequences of these elements, several regions are noticeably conserved. Some of the conserved regions correspond to portions of the transcriptional and self-cleavage domains, while others have not yet been assigned a function. The conservation of satellite 2 observed in these studies suggests that this element arose early during salamander evolution and that the nature of the progenitor of modern day satellite 2 can be inferred from the analysis of this element from a more diverse sample of salamander families. |
