Journal: PLoS ONE
Article Title: Instability of the Octarepeat Region of the Human Prion Protein Gene
Figure Lengend Snippet: Schematic diagrams for analysis of octarepeat mutation rate during PCR or replication in E.coli . (A) Measurement of octarepeat mutants resulting from PCR amplification of octarepeats. Cloned PrP ORF sequences (PrP-Oct5 and PrP-Oct11a) were subjected to PCR with primers HP20 and HP306r. The PCR products (depicted in a shaded box), which contained input (green line) and PCR-mutant (red line) octarepeat sequences as well as “paired” molecules (two parallel lines), were cleaned up and ligated to the pGEM-T vector, producing 4 kinds of ligation products: mutant monomer, wild type monomer, wild type dimer, and mutant dimer. The ligation products were transformed into DH5α competent cells, and the resulting colonies were directly examined by PCR with primers HP50f and HP293r. Plasmid DNAs were extracted from colonies containing mutant octarepeats, subjected to restriction analysis with Sac II and Spe I, and sequenced. The number of mutant colonies over the total number of colonies screened was calculated to represent the octarepeat mutation rate during the PCR process. Small oval: individual E.coli cell; big dashed-line oval: E.coli colony. (B) Measurement of octarepeat mutants resulting from DNA replication in E.coli . pOct5 or pOct11b was used to transform competent DH5α or XL-1 Red E.coli cells, and plasmid DNA sample prepared from a single colony (depicted in a shaded box) was used to transform competent DH5α cells. The mutant colonies (containing only mutant plasmid, red dashed-line oval) and new mutant colonies [containing some cells with the NEW replication-mutant octarepeat insert (light purple), light blue dashed-line oval] were screened out as in (A). The number of mutant colonies (excluding the new mutant colonies) over the total number of colonies examined should reflect the octarepeat mutation rate during the 1 st round of plasmid replication and cell division in E.coli (DH5α or XL-1 Red).
Article Snippet: The PCR products were treated with the Wizard PCR clean-up kit (Promega, WI, USA), ligated to pGEM-T (for Pwo-amplified products, A-tailing was done first with Taq DNA polymerase in PCR buffer with 0.2 mM dATP) and transformed into competent DH5α cells (New England Biolabs, MA, USA) on LB-agar plates with X-gal.
Techniques: Mutagenesis, Polymerase Chain Reaction, Amplification, Clone Assay, Plasmid Preparation, Ligation, Transformation Assay