The fate of the nuclear matrix-associated-region-binding protein SATB1 during apoptosis.
Special AT-rich sequence-binding protein 1 (SATB1), predominantly expressed in thymocytes, was identified as a component of the nuclear matrix protein fraction. Programmed cell death of Jurkat T-cells was induced by various stimuli in Fas-dependent and -independent fashion. During apoptosis, but not during necrosis, SATB1 was cleaved, as rapidly as was lamin B, in a caspase-dependent way yielding a stable 70 kDa fragment. The same result was obtained for apoptotic HL60-cells. We constructed various deletion constructs of SATB1, expressing protein chimeras tagged with green fluorescent protein (GFP). Transient transfection of these into Jurkat or HeLa cells followed by initiation of apoptosis allowed us to map the potential caspase-6 cleavage site VEMD to the N-terminal third of SATB1, leaving an intact DNA-binding domain in the C-terminal part of the protein. Our results suggest that apoptosis-specific breakdown of SATB1, a transcriptional activator of the CD8a gene, might be of physiological relevance during thymic clonal deletion and apoptosis of peripheral T-lymphoid cells.
Gotzmann
J
J
Institute of Tumor Biology - Cancer Research, University of Vienna, A-1090 Vienna, Austria. josef.gotzmann@univie.ac.at
Meissner
M
M
Gerner
C
C
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001665:Binding Sites; D020169:Caspases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D049452:Green Fluorescent Proteins; D018922:HL-60 Cells; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D007700:Kinetics; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D036961:Matrix Attachment Region Binding Proteins; D008969:Molecular Sequence Data; D015530:Nuclear Matrix / Q000378:metabolism*; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; D036961:Matrix Attachment Region Binding Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C076189:SATB1 protein, human; D049452:Green Fluorescent Proteins; D020169:Caspases