Sequence variation of human endogenous retrovirus ERV9-related elements in an env region corresponding to an immunosuppressive peptide: transcription in normal and neoplastic cells.

Evolutionarily conserved sequences corresponding to an immunosuppressive region in retroviral transmembrane proteins were amplified by the polymerase chain reaction from human genomic DNA and reverse-transcribed RNA from one glioma, three pieces of macroscopically normal brain tissue, kidney, lymphocytes, cultured embryonic lung cells, and a rhabdomyosarcoma cell line. Amplification products (125 bp) from DNA and RNA from the glioma and RNA from one normal piece of brain tissue were cloned and sequenced (45 clones). A variety of sequences similar to ERV9 (75 to 93%) were identified. Amplification products were immobilized on nylon filters and hybridized to four different synthetic oligonucleotides derived from the sequenced clones. Sequences without the stop codon seen in ERV9 in this region, possibly encoding functional immunosuppressive proteins, were present in RNA amplificates from all samples. The various cell types showed different hybridization patterns with the four probes. The open reading frame sequences were identified in genomic Southern blots, one probe detecting about 10 copies and another detecting a single copy. Northern (RNA) blots of mRNA from various normal human tissues revealed 2.5-kb (e.g., lung) and 10-kb (e.g., placenta) transcripts hybridizing to one of the probes.