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 Gnathostomata, jawed vertebrates, and they comprise up to 5–8% of the hu ...

es associated with malignant tumors of the testes.

Phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

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 the initial stage of development for 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 ...

, 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 neurons, in the process known as neurodegeneration. Neuronal damage may also ultimately result in their death. Neurodegenerative diseases include amyotrophic lateral sclerosis, mul ...

s such as

amytrophic lateral sclerosis Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND) or—in the United States—Lou Gehrig's disease (LGD), is a rare, terminal neurodegenerative disorder that results in the progressive loss of both upper and lowe ...

(ALS). Endogenous retrovirus K (HERV-K) is related to mammary tumor virus in mice. It exists in the human and

cercopithecoid Old World monkeys are primates in the family Cercopithecidae (). Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons (genus '' Papio''), red colobus (genus '' Piliocolob ...

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. One notable location of HERV-K is the C4 gene of

RCCX RCCX is a complex, multiallelic, and tandem copy number variation (CNV) human DNA locus on chromosome 6p21.3, a cluster located in the major histocompatibility complex (MHC) class III region. CNVs are segments of DNA that vary in copy number ...

module. HERV-K is also found in apes and

Old World monkey Old World monkeys are primates in the family Cercopithecidae (). Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons (genus '' Papio''), red colobus (genus '' Piliocolob ...

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 te ...

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

chimpanzee The chimpanzee (; ''Pan troglodytes''), also simply known as the chimp, is a species of Hominidae, great ape native to the forests and savannahs of tropical Africa. It has four confirmed subspecies and a fifth proposed one. When its close rel ...

s and

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

s, and one with chimpanzees, bonobos and

gorilla Gorillas are primarily herbivorous, terrestrial 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 five su ...

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 In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of 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 ...

(regulator of expression encoded by corf; ) increases

IFITM1 Interferon-induced transmembrane protein 1 is a protein that in humans is encoded by the ''IFITM1'' gene. IFITM1 has also recently been designated CD225 (cluster of differentiation 225). This protein has several additional names: fragilis (human h ...

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 Melanoma is the most dangerous type of skin cancer; it develops from the melanin-producing cells known as melanocytes. It typically occurs in the skin, but may rarely occur in the mouth, intestines, or eye (uveal melanoma). In very rare case ...

cells are closely correlated with

epigenetic In biology, epigenetics is the study of changes in gene expression that happen without changes to the DNA sequence. The Greek prefix ''epi-'' (ἐπι- "over, outside of, around") in ''epigenetics'' implies features that are "on top of" or "in ...

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.

See also

References

Further reading