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A.S. Reichert, D.L. Thurlow, M. Mörl
A Eubacterial Origin for the Human tRNA Nucleotidyltransferase?
tRNA CCAtermini are generated and maintained by tRNA nucleotidyltransferases. Together with poly(A) polymerases and other enzymes they belong to the nucleotidyltransferase superfamily. However, sequence alignments within this family do not allow to distinguish between CCAadding enzymes and poly(A) polymerases. Furthermore, due to the lack of sequence information about animal CCAadding enzymes, identification of corresponding animal genes was not possible so far. Therefore, we looked for the human homolog using the bakers yeast tRNA nucleotidyltransferase as a query sequence in a BLAST search. This revealed that the human gene transcript CGI-47 (#AF151805) deposited in GenBank is likely to encode such an enzyme. To identify the nature of this protein, the cDNA of the transcript was cloned and the recombinant protein biochemically characterized, indicating that CGI-47 encodes a bona fide CCAadding enzyme and not a poly(A) polymerase. This confirmed animal CCAadding enzyme allowed us to identify putative homologs from other animals. Calculation of a neighborjoining tree, using an alignment of several CCAadding enzymes, revealed that the animal enzymes resemble more eubacterial ones than eukaryotic plant and fungal tRNA nucleotidyltransferases, suggesting that the animal nuclear cca genes might have been derived from the endosymbiotic progenitor of mitochondria and are therefore of eubacterial origin.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 382, 10/2001
Pages: 1431 - 1438