Abstract:
DNA polymerase III is a prokaryotic protein, which is usually not found in eukaryotes, however protein sequence databases contain hundreds of entries for eukaryotic proteins labeled or annotated as DNA polymerase III subunit alpha. Horizontal gene transfer and contamination of the eukaryotic sample with a bacterial biological material are among the main likely reasons for this phenomenon. In this project the eukaryotic DNA polymerase III subunit alpha database entries are analyzed to identify whether they are the result of horizontal gene transfer or prokaryotic contamination. A BLAST search of all eukaryotic subunit alpha sequences against a database of prokaryotic genes and genomes was performed and, in some cases, identical or nearly identical matches were found, which is a strong suggestion of the sample contamination. In other cases, only remote homologs of eukaryotic sequences were found in the prokaryotic databases which is suggestive of the
horizontal gene transfer. A phylogenetic investigation revealed likely sources of the transferred genes.
