title: The interactions between SATB1 and F-actin are important for mechanisms of active cell death.
abstract: BACKGROUND
  The direct involvement of nuclear actin filaments in gene transcription and remodeling of chromatin is still debatable. However, nuclear localization of F-actin and its interactions with other nuclear matrix proteins have been reported. The aim of the study was to estimate the interactions between nuclear F-actin and one of the matrix proteins, special AT-rich sequence-binding protein 1 (SATB1), during active cell death induced in vitro by geldanamycin (GA).
  
  
  METHODS
  The expression of SATB1 was modified by the transfection of non-aggressive breast cancer MCF-7 cells with siRNA against SATB1 or expression plasmid with cloned cDNA of SATB1. The amount and localization of F-actin were altered by changes of cofilin-1 (CFL1) expression in MCF-7 cells. The association between SATB1 and F-actin during GA-induced cell death was analyzed using confocal and transmission electron microscopy.
  
  
  RESULTS
  Our studies revealed the colocalization between nuclear F-actin and SATB1 protein, during GA-induced death of breast cancer MCF-7 cells. The colocalization was enhanced in cells with overexpressed SATB1 and cofilin-1. At the ultrastructural level the SATB1 and F-actin complexes were seen at the border of condensed and decondensed chromatin. The presence of SATB1/F-actin molecular complexes was confirmed by magnetic separation of F-actin and interacting proteins.
  
  
  CONCLUSIONS
  We suggest that the molecular interactions between SATB1 and F-actin are necessary for active cell death to occur.
authors: Department and Clinic of Dermatology, Sexually Transmitted Diseases and Immunodermatology, Nicolaus Copernicus University in Torun, Collegium Medicum in Bydgoszcz, Poland. d_gr@me.com.
authors: Dariusz
authors: D
authors: Grzanka
authors: Anna E
authors: AE
authors: Kowalczyk
authors: Magdalena
authors: M
authors: Izdebska
authors: Anna
authors: A
authors: Klimaszewska-Wisniewska
authors: Maciej
authors: M
authors: Gagat
mesh_terms: D000199:Actins / Q000378:metabolism*; D017209:Apoptosis; D016227:Benzoquinones / Q000633:toxicity; D002843:Chromatin / Q000378:metabolism; D006801:Humans; D047029:Lactams, Macrocyclic / Q000633:toxicity; D061986:MCF-7 Cells; D036961:Matrix Attachment Region Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D016227:Benzoquinones; D002843:Chromatin; D047029:Lactams, Macrocyclic; D036961:Matrix Attachment Region Binding Proteins; C076189:SATB1 protein, human; C001277:geldanamycin