SAFB re-distribution marks steps of the apoptotic process.
We have found novel functions of scaffold attachment factor-B1 (SAFB) during apoptosis. The experiments showed that SAFB moved into the nucleolus 15 min after the induction of apoptosis and before the release of cytochrome c into the cytoplasm. Two hours later SAFB formed a peri-nucleolar ring-like structure and this occurred after cytochrome c release and before PARP cleavage. Digestion with RNase suggested that the peri-nucleolar ring structure was dependent on RNA integrity and a RNA moiety formed part of this structure. Studies using SAFB deletion mutants showed that the formation of the peri-nucleolar structure was not mediated by the DNA binding (SAP) or the RNA binding (RRM) domain of SAFB but was instead dependent on the S/K and R/E coiled-coil regions: a result suggesting that the structure is formed via protein interactions. In addition, SAFB cleavage was shown to be mediated by caspase-3 and occurred after the formation of the peri-nucleolar ring and after cleavage of PARP (characteristic of proteins having a direct role in apoptosis). A determinant for this cleavage is located in the DNA binding domain and we hypothesize that SAFB may direct the reorganization and segregation of nuclear RNA and DNA prior to endonuclease-mediated DNA cleavage.
Lee
Youn-Bok
YB
Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, Bristol University, Dorothy Hodgkin Building, Whitson Street Bristol BS1 3NY, UK.
Colley
Shane
S
Norman
Michel
M
Biamonti
Giuseppe
G
Uney
James B
JB
D017209:Apoptosis / Q000187:drug effects; D061945:Caspase Inhibitors; D002466:Cell Nucleolus / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D036961:Matrix Attachment Region Binding Proteins / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D034521:Nuclear Matrix-Associated Proteins / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D011960:Receptors, Estrogen / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology
D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D036961:Matrix Attachment Region Binding Proteins; D050505:Mutant Proteins; D034521:Nuclear Matrix-Associated Proteins; D011960:Receptors, Estrogen; D011993:Recombinant Fusion Proteins; C109132:SAFB protein, human; D019311:Staurosporine