Human endogenous retrovirus K (HERV-K) or Human teratocarcinoma-derived virus (HDTV) is a family of

human endogenous retrovirus Endogenous retroviruses (ERVs) are endogenous viral elements in the genome that closely resemble and can be derived from retroviruses. They are abundant in the genomes of jawed vertebrates, and they comprise up to 5–8% of the human genome ( ...

es associated with malignant tumors of the testes.

Phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

ally, the HERV-K group belongs to the ERV2 or Class II or Betaretrovirus-like supergroup. Over the past several years, it has been found that this group of ERVs play an important role in

embryogenesis An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...

, but their expression is silenced in most cell types in healthy adults. The HERV-K family, and particularly its subgroup HML-2, is the youngest and most transcriptionally active group and hence, it is the best studied among other ERVs. Reactivation of it or anomalous expression of HML-2 in adult tissues has been associated with various types of cancer and with

neurodegenerative disease A neurodegenerative disease is caused by the progressive loss of structure or function of neurons, in the process known as neurodegeneration. Such neuronal damage may ultimately involve cell death. Neurodegenerative diseases include amyotrophic ...

s such as amytrophic lateral sclerosis (ALS). Endogenous retrovirus K (HERV-K) is related to mammary tumor virus in mice. It exists in the human and cercopithecoid genomes. Human genome contains hundreds of copies of HERV-K and many of them possess complete open reading frames (ORFs) that are transcribed and translated, especially in early embryogenesis and in malignancies. HERV-K is also found in apes and

Old World monkey Old World monkey is the common English name for a family of primates known taxonomically as the Cercopithecidae (). Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons ...

s. It is uncertain how long ago in primate evolution the full-length HERV-K proviruses which are in the human genome today were created.M. Barbulescu, G. Turner, M. I. Seaman, A. S. Deinard, K. K. Kidd, ve J. Lenz, “Many human endogenous retrovirus K (HERV-K) proviruses are unique to humans”, Curr. Biol., c. 9, sy 16, ss. 861-S1, Ağu. 1999, doi: 10.1016/S0960-9822(99)80390-X. The human endogenous retrovirus K (HERV-K) was inherited million years ago by the genome of the human ancestors. In 1999 Barbulescu, ''et al.'' showed that, of ten HERV-K

provirus A provirus is a virus genome that is integrated into the DNA of a host cell. In the case of bacterial viruses (bacteriophages), proviruses are often referred to as prophages. However, proviruses are distinctly different from prophages and these ter ...

es cloned, eight were unique to humans, while one was shared with

chimpanzee The chimpanzee (''Pan troglodytes''), also known as simply the chimp, is a species of great ape native to the forest and savannah of tropical Africa. It has four confirmed subspecies and a fifth proposed subspecies. When its close relative th ...

s and

bonobo The bonobo (; ''Pan paniscus''), also historically called the pygmy chimpanzee and less often the dwarf chimpanzee or gracile chimpanzee, is an endangered great ape and one of the two species making up the genus '' Pan,'' the other being the comm ...

s, and one with chimpanzees, bonobos and

gorilla Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four or fi ...

s. Originally, HERV-K was observed by low-stringency hybridization with probes for the mammary tumor virus of the mouse and A particle intracutaneous mouse. In 2015 Grow ''et al.'' demonstrated that HERV-K is transcribed during embryogenesis from the eight cell stage up to the stem cell derivation. Furthermore, overexpression of the HERV-K accessory protein

Rec REC or Rec is a shortening of Recording, the process of capturing data onto a storage medium. REC may also refer to: Educational institutes * Regional Engineering College, colleges of engineering and technology education in India * Rajalakshmi E ...

(regulator of expression encoded by corf; ) increases IFITM1 levels on the cell surface and inhibits viral infection. HERV-K is called, phylogenetically, a supergroup of viruses. It is the only group that reported to contain human-specific members of endogenous retroviruses (ERVs). HERV-K is receptive to microenvironmental modifications and melanoma cells are closely correlated with epigenetic and microenvironmental anomalies. Also the association of HERV-K activation with carcinogenesis is especially interesting.E. Balestrieri vd., “Human Endogenous Retrovirus K in the Crosstalk Between Cancer Cells Microenvironment and Plasticity: A New Perspective for Combination Therapy”, Front. Microbiol., c. 9, 2018, doi:10.3389/fmicb.2018.01448.

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