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Abstract:
Nuclear dimorphism is a unique feature to ciliates that allows the separation of germ and somatic lineage on a nuclear level. The well-established model organism Paramecium tetraurelia harbors two diploid and transcriptionally silent micronuclei (MICs), the germline nuclei, and one highly polyploid and transcriptionally active macronucleus (MAC), the somatic nucleus. Each sexual division the MAC is lost and a new MAC arises from a copy of the MIC. This process requires massive genome rearrangement including genome amplification, chromosome fragmentation and excision of germline-specific sequences. Over 45,000 unique Internally Eliminated Sequences (IESs) are located throughout non-coding and coding regions, necessitating precise excision to guarantee a functional new MAC genome. Though several key players involved in IES elimination have already been identified, many steps in this process remain poorly understood. A chromatin remodeller has been shown to assist the excision of a subset of IESs. Here, two complex partners of this remodeller were identified that participate in IES excision. Their contribution to the complex was verified by localization, co-immunoprecipitation experiments and knockdown studies. Elucidating the composition of this complex will further our understanding of how chromatin remodelling contributes to IES excision.
