Identification of a retrovirus-like repetitive element in human DNA

We describe a 5- to 6-kilobase-pair repetitive family in human DNA. One member of this family is linked to the beta-globin gene cluster and is close to the 3' breakpoints of three different naturally occurring deletions involving this gene cluster. Sequence analysis indicates that this element includes terminal direct repeats of 415 base pairs that exhibit the features of long terminal repeats (LTRs) of retroviruses. A potential histidine tRNA primer binding site occurs just 3' to the 5' direct repeat. This retrovirus-like element interrupts a member of the Kpn I family of repeated DNA and is bracketed by a 5-base-pair directly repeated sequence. When attempts are made to clone the element in bacteriophage, homologous recombination between the LTR-like sequences is very frequently observed. Copy number estimates by two methods indicate that the element is repeated 800-1000 times in the human genome. We term this Homo sapiens family of retrovirus-like elements having a histidine tRNA primer binding site the hsRTVL-H family.