Author/Editor		Lovšin, Nika
Title		Evolucijska dinamika line2 retrotranspozonov pri vretenčarjih
Type		monografija
Place		Ljubljana
Publisher		Medicinska fakulteta
Publication year		2001
Volume		str. 83
Language		slo
Abstract		Eukaryotic genomes contain large amounts of transposable elements (TE) that play crucial roles in genome evolution. Among the most widespread and ancient classes of TEs are non-LTR retrotransposons. LINE2 elements are non-LTR retrotransposons so far identified only in vertebrates. Almost nothing was known about their origin and evolutionary dynamics. LINE2 elements were originally identified in mammals as SINE elements, called MIR. In mammals there are only highly defective copies. The only available full-length LINE2 element has been identified in fish Takifuga rubripes. In our study evolutionary dynamics of LINE2 elements in Deuterostomia has been examined. Genomes of numerous vertebrates and invertebrates have been screened for LINE2 elements, both by PCR and by searching databases. A region containing the reverse transcriptase domain of LINE2 has been amplified and sequenced from the genomes of 15 reptilian species one mammal (Macropus) and one amphibian (Xenopus). Most of the examined LINE2 elements possess insertions, deletions, frameshift mutations and stop codons and only a few reptilian species had intact reverse transcriptase. The presence of LINE2 in reptiles, amphibians, fishes and mammals reveals the widespread distribution of LINE2 in vertebrates. Novel sequence data have been obtained by searching sequence databases. We found LINE2 elements also in invertebrates (sea urchin Strongylocentrotus). So we presume that the LINE2 element was present in the common ancestor of vertebrates and Echinodermata and retained in different lineages over long period of time (600MYA). LINE2 was vertically transmitted from parent to offspring. The absence of LINE2 in turtles, birds, crocodiles and some representatives of mammals and the results of sequence analyses indicate that the evolutionary dynamics of LINE2 is complex. Active copies are present in teleost fishes. (Abstract truncated at 2000 characters).
Descriptors		DNA INSERTION ELEMENTS EVOLUTION, MOLECULAR VERTEBRATES POLYMERASE CHAIN REACTION ESCHERICHIA COLI TRANSFORMATION, GENETIC PLASMIDS BASE SEQUENCE TRANSFECTION AMINO ACID SEQUENCE CLONING, MOLECULAR PHYLOGENY EUKARYOTIC CELLS BACTERIOPHAGES INVERTEBRATES