Abstract
BackgroundCorrect chromosome segregation depends on the sister chromatid cohesion complex. The essential, evolutionarily conserved regulatory protein Irr1/Scc3, is responsible for the complex loading onto DNA and for its removal. We found that, unexpectedly, Irr1 is present not only in the nucleus but also in the cytoplasm.ResultsWe show that Irr1 protein is enriched in the cytoplasm upon arrest of yeast cells in G1 phase following nitrogen starvation, diauxic shift or α-factor action, and also during normal cell cycle. Despite the presence of numerous Crm1-dependent export signals, the cytoplasmic pool of Irr1 is not derived through export from the nucleus but instead is simply retained in the cytoplasm. Cytoplasmic Irr1 interacts with the Imi1 protein implicated in glutathione homeostasis and mitochondrial integrity.ConclusionsBesides regulation of the sister chromatid cohesion complex in the nucleus Irr1 appears to have an additional role in the cytoplasm, possibly through interaction with the cytoplasmic protein Imi1.
Highlights
Correct chromosome segregation depends on the sister chromatid cohesion complex
We describe in more detail the interaction between Irr1 and the cytoplasmic protein Imi1, involved in glutathione homeostasis, which we reported recently [30]
Studying various growth conditions we noticed that the change in Irr1 distribution appeared when the cells ceased exponential growth and was most pronounced in cells subjected to nitrogen starvation
Summary
Correct chromosome segregation depends on the sister chromatid cohesion complex. The essential, evolutionarily conserved regulatory protein Irr1/Scc, is responsible for the complex loading onto DNA and for its removal. An evolutionarily conserved and essential three-subunit DNA-associated protein complex, is an important element which safeguards the accurate segregation, its role is not limited to chromatid cohesion only, as was supposed initially (reviewed in [1, 2]). The cohesin complex tethers sister chromatids together until mitosis onset [3, 4]. It associates with and dissociates from chromosomes and its dynamics depends mainly on the loading complex Scc2–Scc and the regulatory subunits Wapl and Pds5 [3, 5].
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