The novel SAR-binding domain of scaffold attachment factor A (SAF-A) is a target in apoptotic nuclear breakdown.
The scaffold attachment factor A (SAF-A) is an abundant component of the nuclear scaffold and of chromatin, and also occurs in heterogeneous nuclear ribonucleoprotein (hnRNP) complexes. Evidence from previous experiments had suggested that SAF-A most likely has at least two different functions, being involved both in nuclear architecture and RNA metabolism. We now show that the protein has a novel scaffold-associated region (SAR)-specific bipartite DNA-binding domain which is independent from the previously identified RNA-binding domain, the RGG box. During apoptosis, but not during necrosis, SAF-A is cleaved in a caspase-dependent way. Cleavage occurs within the bipartite DNA-binding domain, resulting in a loss of DNA-binding activity and a concomitant detachment of SAF-A from nuclear structural sites. On the other hand, cleavage does not compromise the association of SAF-A with hnRNP complexes, indicating that the function of SAF-A in RNA metabolism is not affected in apoptosis. Our results suggest that detachment of SAF-A from SARs, caused by apoptotic proteolysis of its DNA-binding domain, is linked to the formation of oligonucleosomal-sized DNA fragments and could therefore contribute to nuclear breakdown in apoptotic cells.
Göhring
F
F
Laboratory of Molecular Genetics, Department of Biology, University of Konstanz, 78434 Konstanz, Germany.
Schwab
B L
BL
Nicotera
P
P
Leist
M
M
Fackelmayer
F O
FO
D000595:Amino Acid Sequence; D017209:Apoptosis; D001665:Binding Sites; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D006801:Humans; D019169:Jurkat Cells; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009336:Necrosis; D010446:Peptide Fragments / Q000737:chemistry; D011487:Protein Conformation; D012332:RNA, Heterogeneous Nuclear / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012261:Ribonucleoproteins / Q000737:chemistry* / Q000378:metabolism*
D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D034722:Heterogeneous-Nuclear Ribonucleoprotein U; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D010446:Peptide Fragments; D012332:RNA, Heterogeneous Nuclear; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins