Molecular cloning of a rat chromosome putative recombinogenic sequence homologous to the hepatitis B virus encapsidation signal

Previously, we reported that a 61-bp subgenomic HBV DNA sequence (designated as 15AB, nt 1855-1915) is a hot spot for genomic: recombination and that a cellular protein binding to 15AB may be the putative recombinogenic protein, In the present study, we established the existense of a 15AB-like sequence in human and rat chromosomal DNA by Southern blot analysis, The 15AB-like sequence isolated from the rat chromosome demonstrated a 80.9% identity with 5'-CCAAGCTGTGCCTTGGGTGGC-3', nt 1872-1892 of the hepatitis B virus genome, thought to be the essential region for recombination, Interestingly, this 15AB-like sequence also contained the pentanucleotide motifs GCTGG and CCAGC as an inverted repeat, part of the chi known hot spot for recombination in Escherichia coli, Importantly, a portion of the 15AB-like sequence is homologous (82.1%, 23/28 bp) to break point clusters of the human promyelocytic leukemia (PML) gene, characterized by a translocation [t(15;17)], and to rearranged mouse DNA for the immunoglobulin kappa light chain, Moreover, 15AB and 15AB-like sequences have striking homologies (12/15 = 80.0% and 13/15 = 86.7%, respectively) to the consensus sequence for topoisomerase II, Our present results suggest that this 15AB-like sequence in the rat genome might be a recombinogenic candidate triggering genomic instability in carcinogenesis.