Comprehensive profiling of L1 retrotransposons in mouse.

L1 elements are retrotransposons currently active in mammals. Although L1s are typically silenced in most normal tissues, elevated L1 expression is associated with a variety of conditions, including cancer, aging, infertility and neurological disease. These associations have raised interest in the mapping of human endogenous de novo L1 insertions, and a variety of methods have been developed for this purpose.

Comprehensive profiling of L1 retrotransposons in mouse.

L1 elements are retrotransposons currently active in mammals. Although L1s are typically silenced in most normal tissues, elevated L1 expression is associated with a variety of conditions, including cancer, aging, infertility, and neurological disease. These associations have raised interest in the mapping of human endogenous L1 insertions, and a variety of methods have been developed for this purpose.

Mutation of an L-Type Calcium Channel Gene Leads to T Lymphocyte Dysfunction.

Calcium (Ca) is a vital secondary messenger in T lymphocytes regulating a vast array of important events including maturation, homeostasis, activation, and apoptosis and can enter the cell through CRAC, TRP, and Ca channels. Here we describe a mutation in the L-type Ca channel Ca1.4 leading to T lymphocyte dysfunction, including several hallmarks of immunological exhaustion.

Type 2 Innate Lymphocytes Actuate Immunity Against Tumours and Limit Cancer Metastasis.

Type 2 innate lymphoid cells (ILC2) potentiate immune responses, however, their role in mediating adaptive immunity in cancer has not been assessed. Here, we report that mice genetically lacking ILC2s have significantly increased tumour growth rates and conspicuously higher frequency of circulating tumour cells (CTCs) and resulting metastasis to distal organs. Our data support the model that IL-33 dependent tumour-infiltrating ILC2s are mobilized from the lungs and other tissues through chemoattraction to enter tumours, and subsequently mediate tumour immune-surveillance by cooperating with dendritic cells to promote adaptive cytolytic T cell responses.

A conserved role for the ESCRT membrane budding complex in LINE retrotransposition.

Long interspersed nuclear element-1s (LINE-1s, or L1s) are an active family of retrotransposable elements that continue to mutate mammalian genomes. Despite the large contribution of L1 to mammalian genome evolution, we do not know where active L1 particles (particles in the process of retrotransposition) are located in the cell, or how they move towards the nucleus, the site of L1 reverse transcription. Using a yeast model of LINE retrotransposition, we identified ESCRT (endosomal sorting complex required for transport) as a critical complex for LINE retrotransposition, and verified that this interaction is conserved for human L1.

Discovery of a Metastatic Immune Escape Mechanism Initiated by the Loss of Expression of the Tumour Biomarker Interleukin-33.

A new paradigm for understanding immune-surveillance and immune escape in cancer is described here. Metastatic carcinomas express reduced levels of IL-33 and diminished levels of antigen processing machinery (APM), compared to syngeneic primary tumours. Complementation of IL-33 expression in metastatic tumours upregulates APM expression and functionality of major histocompatibility complex (MHC)-molecules, resulting in reduced tumour growth rates and a lower frequency of circulating tumour cells.

LINE Retrotransposition Assays in Saccharomyces cerevisiae.

Long interspersed nuclear element (LINE) retrotransposons make up significant parts of mammalian genomes. They alter host genomes by direct mutagenesis through integration of new transposon copies, by mobilizing non-autonomous transposons, by changes in host gene activity due to newly integrated transposons and by recombination events between different transposon copies. As a consequence, LINEs can contribute to genetic disease.

Total synthesis of a functional designer eukaryotic chromosome.

Rapid advances in DNA synthesis techniques have made it possible to engineer viruses, biochemical pathways and assemble bacterial genomes. Here, we report the synthesis of a functional 272,871-base pair designer eukaryotic chromosome, synIII, which is based on the 316,617-base pair native Saccharomyces cerevisiae chromosome III. Changes to synIII include TAG/TAA stop-codon replacements, deletion of subtelomeric regions, introns, transfer RNAs, transposons, and silent mating loci as well as insertion of loxPsym sites to enable genome scrambling.

Human LINE-1 restriction by APOBEC3C is deaminase independent and mediated by an ORF1p interaction that affects LINE reverse transcriptase activity.

LINE-1 (L1) retrotransposons are mobile genetic elements whose extensive proliferation resulted in the generation of ≈ 34% of the human genome. They have been shown to be a cause of single-gene diseases. Moreover, L1-encoded endonuclease can elicit double-strand breaks that may lead to genomic instability.

Circular retrotransposition products generated by a LINE retrotransposon.

Non-long terminal repeat (non-LTR) retrotransposons are highly abundant elements that are present in chromosomes throughout the eukaryotic domain of life. The long interspersed nuclear element (LINE-1) (L1) clade of non-LTR retrotransposons has been particularly successful in mammals, accounting for 30-40% of human genome sequence. The current model of LINE retrotransposition, target-primed reverse transcription, culminates in a chromosomally integrated end product.

Characterization of a synthetic human LINE-1 retrotransposon ORFeus-Hs.

Long interspersed elements, type 1(LINE-1, L1) are the most abundant and only active autonomous retrotransposons in the human genome. Native L1 elements are inefficiently expressed because of a transcription elongation defect thought to be caused by high adenosine content in L1 sequences. Previously, we constructed a highly active synthetic mouse L1 element (ORFeus-Mm), partially by reducing the nucleotide composition bias.

Dying for a smoke: how much does differential mortality of smokers affect estimated life-course smoking prevalence?

Objective: An extensive literature uses reconstructed historical smoking rates by birth-cohort to inform anti-smoking policies. This paper examines whether and how these rates change when one adjusts for differential mortality of smokers and non-smokers.

Methods: Using retrospectively reported data from the US (Panel Study of Income Dynamics, 1986, 1999, 2001, 2003, 2005), the UK (British Household Panel Survey, 1999, 2002), and Russia (Russian Longitudinal Monitoring Study, 2000), we generate life-course smoking prevalence rates by age-cohort.

Non-long terminal repeat (non-LTR) retrotransposons: mechanisms, recent developments, and unanswered questions.

Non-long terminal repeat (non-LTR) retrotransposons are present in most eukaryotic genomes. In some species, such as humans, these elements are the most abundant genome sequence and continue to replicate to this day, creating a source of endogenous mutations and potential genotoxic stress. This review will provide a general outline of the replicative cycle of non-LTR retrotransposons.

LINE-like retrotransposition in Saccharomyces cerevisiae.

Over one-third of human genome sequence is a product of non-LTR retrotransposition. The retrotransposon that currently drives this process in humans is the highly abundant LINE-1 (L1) element. Despite the ubiquitous nature of L1's in mammals, we still lack a complete mechanistic understanding of the L1 replication cycle and how it is regulated.

Conditional activation of a single-copy L1 transgene in mice by Cre.

The synthetic L1 retrotransposon, ORFeus, is useful for probing mechanisms of L1 retrotransposition in vivo and for genome-wide mouse mutagenesis because of its high level of activity. To achieve controlled activation of ORFeus in mice, we constructed ORFeus(LSL), in which ORFeus coding sequences were separated from the promoter by a loxP-beta-geo-stop-loxP (LSL) cassette, and derived transgenic mouse lines containing single-copy ORFeus(LSL). We observed tissue-specific ORFeus activation by crossing ORFeus(LSL) to various Cre-expressing lines, specifically in the germ line or the pancreas, providing definite evidence that all host factors and machinery required posttranscriptionally for L1 retrotransposition are available in somatic tissues in living animals.

Active retrotransposition by a synthetic L1 element in mice.

Long interspersed element type 1 (L1) retrotransposons are ubiquitous mammalian mobile elements and potential tools for in vivo mutagenesis; however, native L1 elements are relatively inactive in mice when introduced as transgenes. We have previously described a synthetic L1 element, ORFeus, containing two synonymously recoded ORFs relative to mouse L1. It is significantly more active for retrotransposition in cell culture than all native L1 elements tested.

Gene-breaking: a new paradigm for human retrotransposon-mediated gene evolution.

The L1 retrotransposon is the most highly successful autonomous retrotransposon in mammals. This prolific genome parasite may on occasion benefit its host through genome rearrangements or adjustments of host gene expression. In examining possible effects of L1 elements on host gene expression, we investigated whether a full-length L1 element inserted in the antisense orientation into an intron of a cellular gene may actually split the gene's transcript into two smaller transcripts: (1) a transcript containing the upstream exons and terminating in the major antisense polyadenylation site (MAPS) of the L1, and (2) a transcript derived from the L1 antisense promoter (ASP) that includes the downstream exons of the gene.

LINE-1 retrotransposons: modulators of quantity and quality of mammalian gene expression?

LINE-1 (L1) retrotransposons are replicating repetitive elements that, by mass, are the most-abundant sequences in the human genome. Over one-third of mammalian genomes are the result, directly or indirectly, of L1 retrotransposition. L1 encodes two proteins: ORF1, an RNA-binding protein, and ORF2, an endonuclease/reverse transcriptase.

A highly active synthetic mammalian retrotransposon.

LINE-1 (L1) elements are retrotransposons that comprise large fractions of mammalian genomes. Transcription through L1 open reading frames is inefficient owing to an elongation defect, inhibiting the robust expression of L1 RNA and proteins, the substrate and enzyme(s) for retrotransposition. This elongation defect probably controls L1 transposition frequency in mammalian cells.

Transcriptional disruption by the L1 retrotransposon and implications for mammalian transcriptomes.

LINE-1 (L1) elements are the most abundant autonomous retrotransposons in the human genome, accounting for about 17% of human DNA. The L1 retrotransposon encodes two proteins, open reading frame (ORF)1 and the ORF2 endonuclease/reverse transcriptase. L1 RNA and ORF2 protein are difficult to detect in mammalian cells, even in the context of overexpression systems.