ERV18-1 is an integrated retroviral element of the human genome. It is known that human endogenous retroviruses (ERVs) and ERV-like sequences are part of the repetitive portions of the human genome and are remnants of infections of former exogenous retroviruses. They comprise about 8% of the human genome (Landers et al, 2001) and include solitary long terminal repeats (LTRs), non-retroviral sequences flanked by LTRs, and LTRs-like sequences (Mayer et al, 2011). ERVs are divided into various groups. ERV18-1 is member 1 of the group 18 of endogenous retroviruses and it maps on Chromosome 15, specifically on 15q21.3. In addition, it starts at 53,910,769 and ends at 53,914,712 bp from qter according to Tokuyama et colleagues and other authors (Tokuyama et al, 2018; Mayer et al, 2011). It was detected in human DNA samples from various donors, i.e. male Caucasian, male Asian, female Caucasian. It was also detected, but in less quantity, also from DNA samples of glioma of female Caucasian (Kjellman et al, 1995).

Usually, human ERVs are silenced epigenetically and are not transcribed (Kewitz and Staege, 2013), however, they are found to be transcribed in particular situations, such as under pathological conditions, and usually their transcription is initiated by promoter sequences within the proviral LTRs (Mayer et al, 2011).
ERV18-1 mRNA is 3,916 bp long with a reference sequence reported in GeneBank as AK126787. It is also present in the Ensembl database with a poorly characterized sequence named AC084759.3-201 (ENST00000624468.1). The sequence AK126787 shows 51.3% of GC content. The precise function of ERV18-1 is presently unclear.

No observed pseudogenes for the ERV18-1 sequence.

It is well-known that human ERVs and ERV-like sequences no longer encode proteins because of the accumulation of nonsense mutations as a consequence of their ancient incorporation into the genome of the host (Mayer et al, 2011). In fact, for ERV18-1 sequence there is no protein reported.