Non-LTR retrotransposons such as L1 elements are major components of the mammalian genome, but their mechanism of replication is incompletely understood. Like retroviruses and LTR-containing retrotransposons, non-LTR retrotransposons replicate by reverse transcription of an RNA intermediate. The details of cDNA priming and integration, however, differ between these two classes. In retroviruses,...

Histone H3K9 methylation is required for DNA methylation and silencing of repetitive elements in plants and filamentous fungi. In mammalian cells however, deletion of the H3K9 histone methyltransferases (HMTases) Suv39h1 and Suv39h2 does not affect DNA methylation of the endogenous retrovirus murine leukaemia virus, indicating that H3K9 methylation is dispensable for DNA methylation of retrotra...

LTR retrotransposons and retroviruses are closely related. Although a viral envelope gene is found in some LTR retrotransposons and all retroviruses, only the latter show infectivity. The identification of Ty3-gypsy-like retrotransposons possessing putative envelope-like open reading frames blurred the taxonomical borders and led to the establishment of the Errantivirus, Metavirus and Chromovir...

The sequence corresponding to the first 77 nucleotides of the L1Tc and NARTc non-LTR retrotransposons from Trypanosoma cruzi is an internal promoter (Pr77) that generates abundant, although poorly translatable, un-spliced transcripts. It has been recently described that L1TcRz, an HDV-like ribozyme, resides within the 5'-end of the RNA from the L1Tc and NARTc retrotransposons. Remarkably, the s...

Retrotransposons are mobile genetic elements, and their mobility can lead to genomic instability. Retrotransposon insertions are associated with a diverse range of sporadic diseases, including cancer. Thus, it is not a surprise that multiple host defense mechanisms suppress retrotransposition. The 2',5'-oligoadenylate (2-5A) synthetase (OAS)-RNase L system is a mechanism for restricting viral i...

Retrotransposons outnumber the genes in large plant genomes, thereby comprising the bulk of the genome. They are largely quiescent during development, but become more active under stress conditions. These elements spread throughout the genome by a process termed retrotransposition, which includes transcription of an element into RNA, reverse transcription into cDNA, and reinsertion of the copie...

Terminal-repeat retrotransposons in miniature (TRIMs) are structurally similar to long terminal repeat (LTR) retrotransposons except that they are extremely small and difficult to identify. Thus far, only a few TRIMs have been characterized in the euphyllophytes and the evolutionary and biological impacts and transposition mechanism of TRIMs are poorly understood. In this study, we combined de ...

Although the number of protein-coding genes is not highly variable between plant taxa, the DNA content in their genomes is highly variable, by as much as 2,056-fold from a 1C amount of 0.0648 pg to 132.5 pg. The mean 1C-value in plants is 2.4 pg, and genome size expansion/contraction is lineage-specific in plant taxonomy. Transposable element fractions in plant genomes are also variable, as low...

Transposable elements contribute significantly to plant genome evolution in myriad ways, ranging from local insertional mutations to global effects exerted on genome size through accumulation. Differential accumulation and deletion of transposable elements may profoundly affect genome size, even among members of the same genus. One example is that of Gossypium (cotton), where much of the 3-fold...

Long terminal repeat (LTR) retrotransposons occupy a special place among all mobile genetic element families. The structure of LTR retrotransposons that have three open reading frames is identical to DNA forms of retroviruses that are integrated into the host genome. Several lines of evidence suggest that LTR retrotransposons share a common ancestry with retroviruses and thus are highly relevan...