Contamination of Escherichia coli insertion element DNA sequences in human genome databases

Abstract

During investigation of the molecular mechanism of large DNA fragmentation in apoptosis, we found that one of our clones, which were derived from 30kb DNA fragments generated from heat-treated human cells, mached perfectly with many sequences in E. coli genomic DNA, E. coli cDNA, a Neiserria plasmid, and several human genomic DNAs and cDNAs. All had exactly the same 153bp sequence. In fact, 1147bp DNA, containing the 153bp sequence, was apparently shared between human chromosomes 12, 13, and 21 and E. coli. This DNA was identified as E. coli insertion element 5. We need to pay carefull attention to such contaminations in genome data bases.