HEMO protein
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| HEMO | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Symbol | ERVMER34-1 | ||||||
| Alt. symbols | HEMO, ENVMER34 | ||||||
| NCBI gene | 100288413 | ||||||
| HGNC | 42970 | ||||||
| UniProt | Q9H9K5 | ||||||
| |||||||
HEMO (Human Endogenous MER34 ORF, or ERVMER34-1) is a human endogenous retroviral (HERV) envelope protein encoded by a proviral remnant of the MER34 retrovirus family on chromosome 4.[1] It was identified in 2017 at Institut Gustave Roussy.
The HEMO protein is 563 amino acids in length and retains several structural features of a retroviral envelope protein, including an N-terminal signal peptide, a CWLC motif in the surface (SU) subunit, and a transmembrane domain (TM).[1] Unlike other retroviral envelope proteins, HEMO is non-fusogenic: it has lost its furin cleavage site between the SU and TM subunits as well as its fusion peptide.[2] The gene is transcribed from a cellular CpG island promoter rather than a retroviral long terminal repeat (LTR).[1] A soluble shed form of the protein is released by metalloprotease cleavage upstream of the transmembrane domain, allowing detection in blood plasma.[1]
Overview
The endogenization event for the HEMO retroviral gene is estimated to have occurred more than 100 million years ago (Mya), prior to the divergence of Laurasiatheria and Euarchontoglire.[3]
HEMO is expressed at high levels in the placenta and in embryonic stem cells as well as induced pluripotent stem cells (iPSCs).[1] The shed soluble form is detectable in the blood of pregnant women.[2] In normal somatic tissues, the expression is low. A 2025 study identified BACE2 as a molecular partner of the HEMO protein.[2]