title: Down-regulation of apurinic/apyrimidinic endonuclease expression is associated with the induction of apoptosis in differentiating myeloid leukemia cells.
abstract: The human DNA repair enzyme apurinic/apyrimidinic endonuclease (APE/ref-1) is a multifunctional protein in the DNA base excision repair (BER) pathway that is responsible for repair of apurinic/apyrimidinic (AP) sites in DNA. DNA repair and programmed cell death both function using different mechanisms to protect the organism from the consequences of extensive cellular damage; however, little is known about the relationship of the DNA BER repair pathway to apoptosis. We have determined the relationship of a BER DNA repair enzyme, APE, to apoptosis using the myeloid leukemia cell line HL-60, which can be induced to differentiate down the granulocytic or monocytic/ macrophage pathway. Treatment of HL-60 cells with retinoic acid/DMSO (granulocytic) or phorbol 12-myristate 13-acetate (monocytic) results in apoptosis and in down-regulation of APE expression at both the RNA and protein levels. Moreover, double-labeling experiments using APE immunohistochemistry and the terminal deoxyribonucleotidyl transferase-mediated dUTP-fluorescein nick end labeling assay for apoptosis demonstrate that individual cells undergoing apoptosis lose expression of APE regardless of their state of differentiation. Blocking apoptosis by overexpression of the bcl-2 proto-oncogene in HL-60 cells or by a bcr-abl-related mechanism in K562 cells and subsequent differentiation results in morphological differentiation but no loss of APE expression. These studies establish that down-regulation of APE expression is associated with programmed cell death in cells of the myeloid lineage.
authors.affiliation: Department of Pediatrics, Herman B. Wells Center for Pediatric Research, James Whitcomb Riley Hospital for Children, Indiana University Medical Center, Indianapolis 46202-5225, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Robertson
authors.forename: D P
authors.initials: DP
authors.lastname: Hill
authors.forename: Y
authors.initials: Y
authors.lastname: Xu
authors.forename: L
authors.initials: L
authors.lastname: Liu
authors.forename: S
authors.initials: S
authors.lastname: Van Epps
authors.forename: D M
authors.initials: DM
authors.lastname: Hockenbery
authors.forename: J R
authors.initials: JR
authors.lastname: Park
authors.forename: T M
authors.initials: TM
authors.lastname: Wilson
authors.forename: M R
authors.initials: MR
authors.lastname: Kelley
mesh_terms: D017209:Apoptosis; D002454:Cell Differentiation; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043223:Deoxyribonuclease IV (Phage T4-Induced); D015536:Down-Regulation; D018922:HL-60 Cells; D006801:Humans; D007951:Leukemia, Myeloid / Q000473:pathology*; D008190:Lyases / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology
chemical_list: C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2; D014212:Tretinoin; D043223:Deoxyribonuclease IV (Phage T4-Induced); D008190:Lyases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase