The nucleolar protein nucleophosmin is essential for autophagy induced by inhibiting Pol I transcription

Sci Rep. 2015 Mar 10:5:8903. doi: 10.1038/srep08903.

Abstract

Various cellular stresses activate autophagy, which is involved in lysosomal degradation of cytoplasmic materials for maintaining nutrient homeostasis and eliminating harmful components. Here, we show that RNA polymerase I (Pol I) transcription inhibition induces nucleolar disruption and autophagy. Treatment with autophagy inhibitors or siRNA specific for autophagy-related (ATG) proteins inhibited autophagy but not nucleolar disruption induced by Pol I transcription inhibition, which suggested that nucleolar disruption was upstream of autophagy. Furthermore, treatment with siRNA specific for nucleolar protein nucleophosmin (NPM) inhibited this type of autophagy. This showed that NPM was involved in autophagy when the nucleolus was disrupted by Pol I inhibition. In contrast, NPM was not required for canonical autophagy induced by nutrient starvation, as it was not accompanied by nucleolar disruption. Thus, our results revealed that, in addition to canonical autophagy, there may be NPM-dependent autophagy associated with nucleolar disruption.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Autophagy / genetics*
  • Cell Nucleolus / genetics
  • Humans
  • MCF-7 Cells
  • Nuclear Proteins / antagonists & inhibitors
  • Nuclear Proteins / genetics*
  • Nucleolus Organizer Region / genetics
  • Nucleophosmin
  • RNA Polymerase I / antagonists & inhibitors
  • RNA Polymerase I / genetics*
  • RNA, Small Interfering
  • Transcription, Genetic*

Substances

  • NPM1 protein, human
  • Nuclear Proteins
  • RNA, Small Interfering
  • Nucleophosmin
  • RNA Polymerase I