HERV-R_7q21.2 provirus ancestral envelope (Env) polyprotein is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
that in humans is encoded by the ''ERV3''
gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
.
Function
The human
genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding g ...
includes many retroelements including the human
endogenous retroviruses (HERVs), which compose about 7-8% of the human genome. ERV3, one of the most studied HERVs, is thought to have integrated 30 to 40 million years ago and is present in
higher primate
The simians, anthropoids, or higher primates are an infraorder (Simiiformes ) of primates containing all animals traditionally called monkeys and apes. More precisely, they consist of the parvorders New World monkeys (Platyrrhini) and Catarrh ...
s with the exception of gorillas. Taken together, the observation of genome conservation, the detection of transcript expression, and the presence of conserved
ORFs
ORFS stands for ''Output RF Spectrum'', where 'RF' stands for Radio Frequency.
The acronym ORFS is used in the context of mobile communication systems, e.g., GSM. It stands for the relationship between (a) the frequency offset from the carrier a ...
is circumstantial evidence for a functional role. Similar endogenous retroviral Env genes like
syncytin-1 have important roles in placental formation and embryonic development by enabling cell-cell fusion. Despite its origin as an Env gene, ERV3 has a premature stop codon that precludes any cell-cell fusion functionality. However, it does have an immunosuppressive function that helps the fetus evade a damaging maternal immune response, which may explain its high expression in the placenta.
There is speculation that ERV3 originally did have cell-cell fusion functionality in the placenta, but that it was eventually supplanted by other Env genes like syncytin, leading to a loss of this function.
Another functional role is suggested by the observation that downregulation of ERV3 is reported in
choriocarcinoma
Choriocarcinoma is a malignant, trophoblastic cancer, usually of the placenta. It is characterized by early hematogenous spread to the lungs. It belongs to the malignant end of the spectrum in gestational trophoblastic disease (GTD). It is also c ...
.
References
Further reading
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
External links
*
Transcription factors
{{gene-7-stub