The nucleolar transcriptome regulates Piwi shuttling between the nucleolus and the nucleoplasm.

The nucleolar transcriptome regulates Piwi shuttling between the nucleolus and the nucleoplasm.
Chromosome Res. 2018 Dec 12;:
Authors: Mikhaleva EA, Leinsoo TA, Ishizu H, Gvozdev VA, Klenov MS
Abstract
The nucleolus contains a lot of proteins unrelated to ribosome biogenesis. Some of these proteins shuttle between the nucleolus and the nucleoplasm regulating the cell cycle and stress response. The piRNA binding protein Piwi is involved in silencing of transposable elements (TEs) in the Drosophila gonads. Here we used cultured ovarian somatic cells (OSC) to characterize Piwi as a visitor to the nucleolus. Dynamic Piwi localization was shown to vary from its uniform distribution between the nucleoplasm and the nucleolus to pronounced nucleolar immobilization. We were intrigued by this localization behavior and revealed that nascent nucleolar transcripts recruit Piwi for nucleolar retention. Piwi eviction from the nucleolus was observed upon RNase treatment and after RNA polymerase (Pol) I inhibition, but not after Pol II inactivation. On the contrary, heat shock caused drastic Piwi redistribution from the nucleoplasm to the nucleolus, which occurred only in the presence of Pol I-mediated transcription. These results allow us to hypothesize that specific stress-induced transcripts made by Pol I promote the nucleolar sequestration of proteins in Drosophila, similar to previous observations in mammalian cells. We also found that in OSC, ...

Source: Chromosome Research - December 12, 2018 Category: Genetics & Stem Cells Authors: Mikhaleva EA, Leinsoo TA, Ishizu H, Gvozdev VA, Klenov MS Tags: Chromosome Res Source Type: research