Human endogenous retroviruses (HERVs) are remnants of ancient retroviruses that entered the human genome through ancestral germ cells and became stably integrated into the human DNA. These retroviruses, which are DNA copies of RNA viruses, have become an integral part of the human genome, accounting for approximately 8% of the human genome composition.
HERVs are classified into different families based on their similarities and distinct features. These families include HERV-E, HERV-F, HERV-H, HERV-K, and many others. Each family originates from different retroviral infections that occurred over millions of years of evolution.
Although most HERVs are defective and unable to produce viral particles, they still possess various genetic elements, such as long terminal repeats (LTRs) and open reading frames (ORFs), which indicate their viral origins. These elements can potentially be expressed in specific tissues or under certain conditions, leading to the production of viral proteins or RNA transcripts.
HERVs have been found to play important roles in normal physiological processes as well as in human diseases. They have been implicated in embryonic development, placental formation, and immune response regulation. Aberrant expression or activation of HERVs has also been associated with various pathological conditions, including autoimmune disorders, cancers, and neurological diseases.
Understanding the functions and regulations of HERVs is a complex and ongoing field of research, as they possess the potential to influence human biology in both positive and negative ways. Further exploration of HERVs may provide insights into human evolution, genetic diversity, and the development of novel therapeutic interventions.
