title: The Arabidopsis At1g30680 gene encodes a homologue to the phage T7 gp4 protein that has both DNA primase and DNA helicase activities.
abstract: BACKGROUND
  The Arabidopsis thaliana genome encodes a homologue of the full-length bacteriophage T7 gp4 protein, which is also homologous to the eukaryotic Twinkle protein. While the phage protein has both DNA primase and DNA helicase activities, in animal cells Twinkle is localized to mitochondria and has only DNA helicase activity due to sequence changes in the DNA primase domain. However, Arabidopsis and other plant Twinkle homologues retain sequence homology for both functional domains of the phage protein. The Arabidopsis Twinkle homologue has been shown by others to be dual targeted to mitochondria and chloroplasts.
  
  
  RESULTS
  To determine the functional activity of the Arabidopsis protein we obtained the gene for the full-length Arabidopsis protein and expressed it in bacteria. The purified protein was shown to have both DNA primase and DNA helicase activities. Western blot and qRT-PCR analysis indicated that the Arabidopsis gene is expressed most abundantly in young leaves and shoot apex tissue, as expected if this protein plays a role in organelle DNA replication. This expression is closely correlated with the expression of organelle-localized DNA polymerase in the same tissues. Homologues from other plant species show close similarity by phylogenetic analysis.
  
  
  CONCLUSIONS
  The results presented here indicate that the Arabidopsis phage T7 gp4/Twinkle homologue has both DNA primase and DNA helicase activities and may provide these functions for organelle DNA replication.
authors: Dept. of Microbiology & Molecular Biology, 775 WIDB, Brigham Young University, Provo, UT 84602, USA.
authors: Joann
authors: J
authors: Diray-Arce
authors: Bin
authors: B
authors: Liu
authors: John D
authors: JD
authors: Cupp
authors: Travis
authors: T
authors: Hunt
authors: Brent L
authors: BL
authors: Nielsen
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D017123:Bacteriophage T7 / Q000201:enzymology*; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D019915:DNA Primase / Q000235:genetics / Q000378:metabolism*; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D014759:Viral Envelope Proteins; D019915:DNA Primase; D004265:DNA Helicases