HERV-H LTR Associating Protein 2 (HHLA2)

Human endogenous retrovirus (HERV) sequences are repetitive elements, derived from ancient germline retroviral infections, that have increased in copy number by further rounds of infection, retrotransposition, and/or duplication. The HERV-H family has been shown to play a role in the expression of a variety of adjacent genes.

HHLA2 encodes a predicted 414-amino acid protein with a secretory signal peptide, 3 immunoglobulin-like domains, and a transmembrane domain. Northern blot analysis showed that HHLA2 is expressed primarily in intestinal tissues, kidney, and lung as an approximately 2.5-kb transcript. RT-PCR experiments also detected transcription in brain, placenta, and lymphocytes. No major human HHLA2 or HHLA3 transcripts that utilized a non-LTR polyadenylation signal were detected.