Characterization of a cDNA encoding a novel plant poly(A) polymerase.
We have isolated cDNA clones encoding a novel factor (PAP-I) that is a component of a multi-subunit poly(A) polymerase from pea seedlings. The encoded protein, when isolated from appropriately engineered Escherichia coli, was active as a poly(A) polymerase, either with an associated RNA binding cofactor (PAP-III) or with free poly(A) as an RNA substrate. The latter observation indicates that PAP-I is in fact a poly(A) polymerase. PAP-I bore a striking resemblance to an as yet uncharacterized cyanobacterial protein. This observation suggested a possible chloroplast localization for PAP-I. This hypothesis was tested and found to be substantiated; immunoblot analysis identified PAP-I in chloroplast but not nuclear extracts. Our results suggest that PAP-I is a component of the machinery that adds poly(A) to chloroplast RNAs.
Department of Agronomy, University of Kentucky, Lexington 40546-0091, USA.
J
J
Das Gupta
Q S
QS
Li
A B
AB
Thomson
A G
AG
Hunt
D000595:Amino Acid Sequence; D001483:Base Sequence; D002736:Chloroplasts / Q000201:enzymology; D018076:DNA, Complementary / Q000235:genetics* / Q000302:isolation & purification; D018744:DNA, Plant / Q000235:genetics* / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics; D008969:Molecular Sequence Data; D018532:Pisum sativum / Q000201:enzymology* / Q000235:genetics*; D011062:Polynucleotide Adenylyltransferase / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D018744:DNA, Plant; D011993:Recombinant Fusion Proteins; D011062:Polynucleotide Adenylyltransferase