A mating-type mutagenesis screen identifies a zinc-finger protein required for specific DNA excision events in Paramecium

Bhullar, Simran; Denby Wilkes, Cyril; Arnaiz, Olivier; Nowacki, Mariusz; Sperling, Linda; Meyer, Eric (2018). A mating-type mutagenesis screen identifies a zinc-finger protein required for specific DNA excision events in Paramecium. Nucleic acids research, 46(18), pp. 9550-9562. Oxford University Press 10.1093/nar/gky772

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In the ciliate Paramecium tetraurelia, functional genes are reconstituted during development of the somatic macronucleus through the precise excision of ∼45 000 single-copy Internal Eliminated Sequences (IESs), thought to be the degenerate remnants of ancient transposon insertions. Like introns, IESs are marked only by a weak consensus at their ends. How such a diverse set of sequences is faithfully recognized and precisely excised remains unclear: specialized small RNAs have been implicated, but in their absence up to ∼60% of IESs are still correctly excised. To get further insight, we designed a mutagenesis screen based on the hypersensitivity of a specific excision event in the mtA gene, which determines mating types. Unlike most IES-containing genes, the active form of mtA is the unexcised one, allowing the recovery of hypomorphic alleles of essential IES recognition/excision factors. Such is the case of one mutation recovered in the Piwi gene PTIWI09, a key player in small RNA-mediated IES recognition. Another mutation identified a novel protein with a C2H2 zinc finger, mtGa, which is required for excision of a small subset of IESs characterized by enrichment in a 5-bp motif. The unexpected implication of a sequence-specific factor establishes a new paradigm for IES recognition and/or excision.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Department of Biology > Institute of Cell Biology > Ciliate
08 Faculty of Science > Department of Biology > Institute of Cell Biology

UniBE Contributor:

Bhullar, Simran and Nowacki, Mariusz

Subjects:

500 Science > 570 Life sciences; biology

ISSN:

0305-1048

Publisher:

Oxford University Press

Language:

English

Submitter:

Mariusz Nowacki

Date Deposited:

30 Aug 2018 10:16

Last Modified:

25 Oct 2019 12:58

Publisher DOI:

10.1093/nar/gky772

BORIS DOI:

10.7892/boris.119691

URI:

https://boris.unibe.ch/id/eprint/119691

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