Retrotransposons play an important role in the evolution of genomic structure and function. Here we report on the characterization of a novel retrotransposon called kangaroo from the multicellular green alga, Volvox carteri. kangaroo elements are highly mobile and their expression is developmentally regulated. They probably integrate via double-stranded, closed-circle DNA intermediates through ...

Retrotransposons are mobile genetic elements abundant in plant and animal genomes. While efficiently silenced by the epigenetic machinery, they can be reactivated upon stress or during development. Their level of transcription not reflecting their transposition ability, it is thus difficult to evaluate their contribution to the active mobilome. Here we applied a simple methodology based on the ...

Although the proliferation of LTR retrotransposons can cause major genomic modification and reorganization, the evolutionary dynamics that affect their frequency in host genomes are poorly understood. We analyzed patterns of genetic variation among LTR retrotransposons from Oryza sativa to investigate the type of selective forces that potentially limit their amplification and subsequent populat...

HeT-A elements are non-long terminal repeat (non-LTR) retrotransposons found in head-to-tail arrays on Drosophila chromosome ends, where they form telomeres. We report that HeT-A promoter activity is located in the 3' end of the element, unlike the 5' location seen for other non-LTR retrotransposons. In HeT-A arrays the 3' sequence of one element directs transcription of its downstream neighbor...

Complex genome organizations participate in various nuclear processes including transcription, DNA replication, and repair. However, the mechanisms that generate and regulate these functional genome structures remain largely unknown. Here, we describe how the Ku heterodimer complex, which functions in nonhomologous end joining, mediates clustering of long terminal repeat retrotransposons at cen...

The factors guiding retrotransposon insertion site preference are not well understood. Different types of retrotransposons share common replication machinery and yet occupy distinct genomic domains. Autonomous long interspersed elements accumulate in gene-poor domains and their nonautonomous short interspersed elements accumulate in gene-rich domains. To determine genomic factors that contribut...

Retrotransposons are mobile DNA elements present throughout eukaryotic genomes that can cause mutations and genome rearrangements when they replicate through reverse transcription. Increased expression and/or mobility of retrotransposons has been correlated with aging in yeast, Caenorhabditis elegans, Drosophila melanogaster, and mammals. The many copies of retrotransposons in humans and variou...

Retroviruses and long terminal repeat (LTR) retrotransposons share a common structural organization. The main difference between these retroelements is the presence of a functional envelope (env) gene in retroviruses, which is absent or nonfunctional in LTR retrotransposons. Several similarities between these two groups of retroelements have been detected for the reverse transcriptase, gag, and...

The genomes of representative species of fishes, amphibians, and reptiles contain non-long-terminal-repeat (non-LTR) retrotransposons showing strong sequence identity to the chicken repeat 1 (CR1) non-LTR retrotransposon from birds. These nonavian retroelements have been termed CR1-like elements. We have isolated sequences of a non-LTR retrotransposon from the human blood fluke Schistosoma mans...

Reverse transcriptases have shaped genomes in many ways. A remarkable example of this shaping is found on telomeres of the genus Drosophila, where retrotransposons have a vital role in chromosome structure. Drosophila lacks telomerase; instead, three telomere-specific retrotransposons maintain chromosome ends. Repeated transpositions to chromosome ends produce long head to tail arrays of these ...