Fig. 1

Arabidopsis Pol1A, Pol1B, Twinkle, SSB1, E. coli DNA polymerase I, and T7 gp4. “SP” stands for “signal peptide” as predicted by the SignalP server. Functional domains are illustrated based on results from the NCBI conserved domain database, Uniprot [57] databases and published works by Bernstein [58], Gray [15] and Richardson [59]. Signal peptide regions were predicted using the SignalP [60] server. With the exception of SSB1, these proteins are unusually large, especially when compared to the length of orthologous plant and animal proteins that function in the nucleus [61]. The light green region in Pol1A and Pol1B represents the border of the plastid-like DNA pol a domain which overlaps with the dark green region representing the more general DNA pol a domain. Genes are shown to scale in terms of cDNA and amino acid length. Black arrows represent PCR primers used to create truncations for each protein. Note that in our yeast-two-hybrid experiment, all potential truncations were tested against each other simultaneously by creating truncation libraries in haploid yeast which were mated and grown on selective media