Small Things Considered: Polintons; A Viral Missing Link?

The line between viruses and parasitic elements of the genome is thin and delicate, and probably often crossed. Parasitic elements that acquire the means to escape the host cell become viruses and, conversely, viruses can lose this ability and return to a more limited lifestyle as transposable elements (TEs). This back-and-forth occurs alongside a propensity for gene exchange, with genes acquired horizontally from various hosts, and at various periods of evolution.The result is that, although viruses and other "selfish" elements are obviously related, their relationship cannot be represented by the satisfying, graceful branches seen on phylogenetic trees depicting the evolution of more pedestrian organisms such as primates, for example. Instead, a virus or TE is like a quilt whose patches were added by different quilters, at different times. 

Futurity.org – Rogue DNA busts out of aging cell ‘prison’

As cells age, they lose control over parasitic strands of mobile DNA that insert themselves into chromosomes, new research shows.The parasitic strands of genetic material called transposable elements—transposons—lurk in our chromosomes, poised to wreak genomic havoc. Cells have evolved ways to defend themselves, but in the new study, researchers describe how cells lose this ability as they age, possibly resulting in a decline in their function and health.

Storm of 'awakened' transposons may cause brain-cell pathologies in ALS, other illnesses

A team of neuroscientists and informatics experts at Cold Spring Harbor Laboratory (CSHL) reports important progress in an effort to understand the relationship between transposons -- sequences of DNA that can jump around within the genome, potentially causing great damage -- and mechanisms involved in serious neurodegenerative disorders including ALS (amyotrophic lateral sclerosis, also known as Lou Gehrig's disease), FTLD (frontotemporal lobar degeneration) and Alzheimer's disease.