TRANSCRIPTION OF HERV-K-RELATED LTRS IN HUMAN PLACENTA AND LEUKEMIC-CELLS

The human genome contains a family of endogenous retroviruses, HERV-K, with sequence homology to the B-type mouse mammary tumor virus (MMTV) . We have detected HERV-K-LTR related cDNA clones by screening a human placenta cDNA library with a HERV-K LTR probe. Three of the isolated cDNA clones were characterized by nucleotide sequencing. The analyzed clones did not contain any retroviral sequences other than those relat ed to HERV-K LTRs, but were found to be coexpressed with cellular sequ ences. Furthermore, transcripts containing HERV-K LTR sequences were d emonstrated by Northern blotting and PCR in human leukemic and normal white blood cells, as well as in various tumor cell lines, indicating abundant transcription of solitary HERV-K LTRs in human tissues. In pa tients with lymphatic leukemias, a transcript of about 6 kb hybridizin g with HERV-K LTR was detected that was not found in with myelogenous leukemias or in patients healthy persons.