Mapping the Single Origin of Replication in the Naegleria gruberi Extrachromosomal DNA Element

We reported elsewhere the molecular cloning and the complete sequence analysis of the entire rRNA gene-containing element of N. gruberi (strain EGB). Using neutral/neutral two-dimensional agarose electrophoresis, the region in the element enclosing the single replication origin using DNA from asynchronous and axenically propagated N. gruberi populations was localized within a 2.1 kbp fragment located approximately 2,300 bp from the 18S rRNA gene and 3,700 bp from the 28S rRNA gene. The results indicate that replication occurs from a single origin via a theta-type mode of replication rather than by a rolling circle mode. Further, G-quadruplex elements, often located near DNA replication origins, occur in and near this fragment in a repeated sequence.
Source: Protist - Category: Molecular Biology Source Type: research