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The CCA‐adding enzyme: A central scrutinizer in tRNA quality control
Author(s) -
Betat Heike,
Mörl Mario
Publication year - 2015
Publication title -
bioessays
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.175
H-Index - 184
eISSN - 1521-1878
pISSN - 0265-9247
DOI - 10.1002/bies.201500043
Subject(s) - transfer rna , enzyme , sequence (biology) , nucleotidyltransferase , rna , biochemistry , chemistry , stereochemistry , biology , gene
tRNA nucleotidyltransferase adds the invariant CCA‐terminus to the tRNA 3′‐end, a central step in tRNA maturation. This CCA‐adding enzyme is a specialized RNA polymerase that synthesizes the CCA sequence at high fidelity in all kingdoms of life. Recently, an additional function of this enzyme was identified, where it generates a specific degradation tag on structurally unstable tRNAs. This tag consists of an additional repeat of the CCA triplet, leading to a 3′‐terminal CCACCA sequence. In order to explain how the enzyme catalyzes this extended polymerization reaction, Kuhn et al. solved a series of co‐crystal structures of the CCA‐adding enzyme from Archaeoglobus fulgidus in complex with different tRNA substrates. They show that the enzyme forces a bound unstable tRNA to refold the acceptor stem for a second round of CCA‐addition, while stable transcripts are robust enough to resist this isomerization. In this review, we discuss how the CCA‐adding enzyme uses a simple yet very elegant way to scrutinize its substrates for sufficient structural stability and, consequently, functionality.