L1H

L1H, also known as the long interspersed nuclear element 1 (LINE-1) human, refers to the human subfamily of LINE-1 retrotransposons. These are mobile genetic elements that make up a significant portion of the human genome. LINE-1 elements are autonomous retrotransposons, meaning they encode the proteins necessary for their own transposition, including reverse transcriptase and endonuclease. This allows them to "copy and paste" themselves to new locations in the genome through an RNA intermediate and reverse transcription.

While the majority of LINE-1 elements in the human genome are truncated and inactive, a small percentage are full-length and potentially capable of retrotransposition. The activity of these elements is generally suppressed by cellular mechanisms, but under certain conditions, such as during development or in disease states like cancer, LINE-1 activity can be reactivated. This reactivation can lead to genomic instability through insertional mutagenesis, where the insertion of a new LINE-1 element disrupts gene function or regulation. It can also cause DNA double-strand breaks.

The study of L1H is important for understanding genome evolution, gene regulation, and the pathogenesis of various diseases. Research focuses on identifying the factors that control L1H activity and how this activity contributes to human health and disease.