2023  1,500
2022  1,200
2021  1,540
2020  1,374
2019  1,023
2018  0,932
2017  0,977
2016  0,799
2015  0,662
2014  0,740
2013  0,739
2012  0,637
2011  0,658
2010  0,654
2009  0,570
2008  0,849
2007  0,805
2006  0,330
2005  0,435
2004  0,623
2003  0,567
2002  0,641
2001  0,490
2000  0,477
1999  0,762
1998  0,785
1997  0,507
1996  0,518
1995  0,502
Vol 49(2015) N 1 p. 161-167; DOI 10.1134/S0026893315010100 Full Text

E.A. Mikhaleva, E.Y. Yakushev, A.D. Stolyarenko, M.S. Klenov, Ya.M. Rozovsky, V.A. Gvozdev*

Piwi protein as a nucleolus visitor in Drosophila melanogaster

Institute of Molecular Genetics, Russian Academy of Sciences, Moscow, 123182 Russia

Received - 2014-08-03; Accepted - 2014-08-17

The evolutionarily conserved nuclear Piwi protein of Drosophila melanogaster is the defining member of the Argonaute small RNA-binding protein family. Guided by piRNAs, Piwi functions in transposon silencing in somatic and germ cells of gonads. We found that in ovarian somatic and germ cells, as well as in the established ovarian somatic cell line, Piwi accumulates predominantly in the nucleolus, the main nuclear compartment which participates not only in rRNA synthesis, but also in various cell stress responses. We have shown the colocalization of Piwi with the nucleolar marker proteins fibrillarin and Nopp140. The piwiNt mutation which prevents the transport of Piwi to the nucleus and disrupts transposon silencing led to 6-8 fold upregulation of rRNA gene expression, as assessed by the level of transcripts of transposon insertions in 28S rRNA genes. RNase treatment of live cultured ovarian somatic cells depleted Piwi from the nucleolus. The same effect was observed upon inhibition of the activity of RNA polymerase I, which transcribes rRNA genes, but not RNA polymerase II. In contrast, upon heat shock, Piwi concentrated in the nucleolus and was depleted from the nucleoplasm. These results implicate Piwi in RNA polymerase I activity modulation and stress response in the nucleolus. Possible noncanonical Piwi functions are discussed, which are not related to the role of Piwi in transposon silencing.

nucleolus, Piwi protein, rDNA, RNA polymerase I, rRNA