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A paralog of Pcc1 is the fifth core subunit of the KEOPS tRNA-modifying complex in Archaea

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Daugeron, Marie-Claire | Missoury, Sophia | da Cunha, Violette | Lazar, Noureddine | Collinet, Bruno | van Tilbeurgh, Herman | Basta, Tamara

Edité par CCSD ; Nature Publishing Group -

International audience. In Archaea and Eukaryotes, the synthesis of a universal tRNA modification, N$^6$ -threonyl-carbamoyl adenosine (t$^6$A), is catalyzed by the KEOPS complex composed of Kae1, Bud32, Cgi121, and Pcc1. A fifth subunit, Gon7, is found only in Fungi and Metazoa. Here, we identify and characterize a fifth KEOPS subunit in Archaea. This protein, dubbed Pcc2, is a paralog of Pcc1 and is widely conserved in Archaea. Pcc1 and Pcc2 form a heterodimer in solution, and show modest sequence conservation but very high structural similarity. The five-subunit archaeal KEOPS does not form dimers but retains robust tRNA binding and t$^6$A synthetic activity. Pcc2 can substitute for Pcc1 but the resulting KEOPS complex is inactive, suggesting a distinct function for the two paralogs. Comparative sequence and structure analyses point to a possible evolutionary link between archaeal Pcc2 and eukaryotic Gon7. Our work indicates that Pcc2 regulates the oligomeric state of the KEOPS complex, a feature that seems to be conserved from Archaea to Eukaryotes.

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