Gene transfer from mitochondrion to nucleus: novel mechanisms for gene activation from Cox2.
The evolutionarily recent transfer of the gene for cytochrome c oxidase subunit 2 (cox2) from the mitochondrion to the nucleus in legumes is shown to have involved novel gene-activation steps. The acquired mitochondrial targeting presequence is bordered by two introns. Characterization of the import of soybean Cox2 indicates that the presequence is cleaved in a three-step process which is independent of assembly. The final processing step takes place only in the mitochondria of legume species, and not in several non-legume plants. The unusually long presequence of 136 amino acids consists of three regions: the first 20 amino acids are required for mitochondrial targeting and can be replaced by another presequence; the central portion of the presequence is required for efficient import of the Cox2 protein into mitochondria; and the last 12 amino acids, derived from the mitochondrially encoded protein, are required for correct maturation of the imported protein. The acquisition of a unique presequence, and the capacity for legume mitochondria to remove this presequence post-import, are considered to be essential adaptations for targeting of Cox2 to the mitochondrion and therefore activation of the transferred gene in the nucleus.
Daley
Daniel O
DO
Department of Biochemistry, University of Western Australia, Nedlands 6907, Australia.
Adams
Keith L
KL
Clifton
Rachel
R
Qualmann
Svenja
S
Millar
A Harvey
AH
Palmer
Jeffrey D
JD
Pratje
Elke
E
Whelan
James
J
D000595:Amino Acid Sequence; D001692:Biological Transport; D015153:Blotting, Western; D002467:Cell Nucleus / Q000201:enzymology / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics* / Q000378:metabolism; D017353:Gene Deletion; D018506:Gene Expression Regulation, Plant; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D013025:Glycine max / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D013045:Species Specificity; D015533:Transcriptional Activation
D010940:Plant Proteins; D003576:Electron Transport Complex IV