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Macromolecular crowding effect is critical for maintaining SIRT1's nuclear localization in cancer cells

Lidong Sun1, Jia Fang1

  • 1a Department of Tumor Biology , H. Lee Moffitt Cancer Center and Research Institute , Tampa , FL , USA.

Cell Cycle (Georgetown, Tex.)
|July 28, 2016
PubMed

Insights

SIRT1, a key protein deacetylase, is predominantly found in the nucleus of cancer cells. This study clarifies inconsistent localization reports by refining cell fractionation methods to prevent cytoplasmic leakage.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Background:

  • Sirtuin 1 (SIRT1) is a crucial class III histone deacetylase involved in cellular stress responses, development, and cancer.
  • SIRT1's role in deacetylating various nuclear and cytoplasmic proteins is well-established, but its precise subcellular localization in cancer cells remains debated.

Purpose of the Study:

  • To investigate the reasons behind inconsistent reports on SIRT1 subcellular localization in cancer cells.
  • To develop and validate an improved cell fractionation method that accurately reflects SIRT1's native localization.

Main Methods:

  • Comparative analysis of immunofluorescence, live cell imaging, and conventional cell fractionation techniques.
  • Development of an optimized cell fractionation protocol addressing issues like loss of macromolecular crowding and hypotonic dwelling.
  • Application of the improved method across diverse human cancer cell lines.

Main Results:

  • Inconsistent SIRT1 localization reports stem from artifacts introduced during conventional cell fractionation, causing cytoplasmic leakage.
  • Immunofluorescence and live cell imaging suggest nuclear localization, but this can be obscured by fractionation artifacts.
  • The refined cell fractionation procedure successfully preserved SIRT1's native subcellular distribution, confirming predominant nuclear localization.

Conclusions:

  • SIRT1 predominantly localizes to the nucleus in human cancer cells.
  • Artifacts during sample preparation can lead to misinterpretation of SIRT1's subcellular localization.
  • The developed improved fractionation method provides a more accurate assessment of SIRT1 localization in cancer research.
Keywords:
SIRT1cancerhistone deacetylasesnuclear localizationprotein fractionation

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