The evidence for increased L1 activity in the site of human adult brain neurogenesis.

Retroelement activity is a common source of polymorphisms in human genome. The mechanism whereby retroelements contribute to the intraindividual genetic heterogeneity by inserting into the DNA of somatic cells is gaining increasing attention. Brain tissues are suspected to accumulate genetic heterogeneity as a result of the retroelements somatic activity.

Next generation sequencing for TCR repertoire profiling: platform-specific features and correction algorithms.

The TCR repertoire is a mirror of the human immune system that reflects processes caused by infections, cancer, autoimmunity, and aging. Next generation sequencing (NGS) is becoming a powerful tool for deep TCR profiling; yet, questions abound regarding the methodological approaches for sample preparation and correct data interpretation. Accumulated PCR and sequencing errors along with library preparation bottlenecks and uneven PCR efficiencies lead to information loss, biased quantification, and generation of huge artificial TCR diversity.

Long L1 insertions in human gene introns specifically reduce the content of corresponding primary transcripts.

LINE-1 (L1) retrotransposons comprise about 17% of the human genome and include a recently transposed set of Ta-L1 elements that are polymorphic in humans. Although it is widely believed that L1s play an essential role in shaping and functioning of mammalian genomes, the understanding of the impact of L1 insertions on gene expression is far from being comprehensive. Here we compared hnRNA contents for allele pairs of genes heterozygous for Ta-L1 insertions in their introns in human cell lines of various origin.

Cell line fingerprinting using retroelement insertion polymorphism.

Human cell lines are an indispensable tool for functional studies of living entities in their numerous manifestations starting with integral complex systems such as signal pathways and networks, regulation of gene ensembles, epigenetic factors, and finishing with pathological changes and impact of artificially introduced elements, such as various transgenes, on the behavior of the cell. Therefore, it is highly desirable to have reliable cell line identification techniques to make sure that the cell lines to be used in experiments are exactly what is expected. To this end, we developed a set of informative markers based on insertion polymorphism of human retroelements (REs).

The human genome contains many types of chimeric retrogenes generated through in vivo RNA recombination.

L1 retrotransposons play an important role in mammalian genome shaping. In particular, they can transduce their 3'-flanking regions to new genomic loci or produce pseudogenes or retrotranscripts through reverse transcription of different kinds of cellular RNAs. Recently, we found in the human genome an unusual family of chimeric retrotranscripts composed of full-sized copies of U6 small nuclear RNAs fused at their 3' termini with 5'-truncated, 3'-poly(A)-tailed L1s.

Human-specific subfamilies of HERV-K (HML-2) long terminal repeats: three master genes were active simultaneously during branching of hominoid lineages.

Using 40 known human-specific LTR sequences, we have derived a consensus sequence for an evolutionary young HERV-K (HML-2) LTR family, which was named the HS family. In the human genome the HS family is represented by approximately 150-160 LTR sequences, 90% of them being human-specific (hs). The family can be subdivided into two subfamilies differing in five linked nucleotide substitutions: HS-a and HS-b of 5.

Genome-wide targeted search for human specific and polymorphic L1 integrations.

Retroelements (REs) occupy up to 40% of the human genome. Newly integrated REs can change the pattern of expression of pre-existing host genes and therefore might play a significant role in evolution. In particular, human- and primate-specific REs could affect the divergence of the Hominoidea superfamily.

A new family of chimeric retrotranscripts formed by a full copy of U6 small nuclear RNA fused to the 3' terminus of l1.

Long interspersed nuclear elements (LINE-1, L1) constitute a large family of mammalian retrotransposons that have been replicating and evolving in mammals for more than 100 million years and now compose 17% of the human genome. They have an important creative role in human genomic evolution through mechanisms such as new integrations, generation of processed pseudogenes, and transfer of non-L1 DNA flanking their 3' ends to new genomic locations. Here we present evidence that the L1 integration machinery was used for the creation of a new family of chimeric retrotranscripts, which contain a full copy of U6 small nuclear RNA and a 3' part of L1 at their 5' and 3' ends, respectively.