Functional diversification of Paramecium Ku80 paralogs safeguards genome integrity during precise programmed DNA elimination

Autoři: Arthur Abello aff001;  Vinciane Régnier aff001;  Olivier Arnaiz aff001;  Romain Le Bars aff001;  Mireille Bétermier aff001;  Julien Bischerour aff001
Působiště autorů: Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France aff001;  Université de Paris, Paris, France aff002
Vyšlo v časopise: Functional diversification of Paramecium Ku80 paralogs safeguards genome integrity during precise programmed DNA elimination. PLoS Genet 16(4): e32767. doi:10.1371/journal.pgen.1008723
Kategorie: Research Article
doi: 10.1371/journal.pgen.1008723


Gene duplication and diversification drive the emergence of novel functions during evolution. Because of whole genome duplications, ciliates from the Paramecium aurelia group constitute a remarkable system to study the evolutionary fate of duplicated genes. Paramecium species harbor two types of nuclei: a germline micronucleus (MIC) and a somatic macronucleus (MAC) that forms from the MIC at each sexual cycle. During MAC development, ~45,000 germline Internal Eliminated Sequences (IES) are excised precisely from the genome through a ‘cut-and-close’ mechanism. Here, we have studied the P. tetraurelia paralogs of KU80, which encode a key DNA double-strand break repair factor involved in non-homologous end joining. The three KU80 genes have different transcription patterns, KU80a and KU80b being constitutively expressed, while KU80c is specifically induced during MAC development. Immunofluorescence microscopy and high-throughput DNA sequencing revealed that Ku80c stably anchors the PiggyMac (Pgm) endonuclease in the developing MAC and is essential for IES excision genome-wide, providing a molecular explanation for the previously reported Ku-dependent licensing of DNA cleavage at IES ends. Expressing Ku80a under KU80c transcription signals failed to complement a depletion of endogenous Ku80c, indicating that the two paralogous proteins have distinct properties. Domain-swap experiments identified the α/β domain of Ku80c as the major determinant for its specialized function, while its C-terminal part is required for excision of only a small subset of IESs located in IES-dense regions. We conclude that Ku80c has acquired the ability to license Pgm-dependent DNA cleavage, securing precise DNA elimination during programmed rearrangements. The present study thus provides novel evidence for functional diversification of genes issued from a whole-genome duplication.

Klíčová slova:

Cell fusion – DNA cleavage – Chromatin – Immunostaining – Protein domains – RNA interference – Sequence alignment – Paramecium


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