Barrier-to-autointegration factor: major roles in chromatin decondensation and nuclear assembly.
Barrier-to-autointegration factor (BAF) is a DNA-bridging protein, highly conserved in metazoans. BAF binds directly to LEM (LAP2, emerin, MAN1) domain nuclear membrane proteins, including LAP2 and emerin. We used site-directed mutagenesis and biochemical analysis to map functionally important residues in human BAF, including those required for direct binding to DNA or emerin. We also tested wild-type BAF and 25 point mutants for their effects on nuclear assembly in Xenopus egg extracts, which contain approximately 12 microM endogenous BAF dimers. Exogenous BAF caused two distinct effects: at low added concentrations, wild-type BAF enhanced chromatin decondensation and nuclear growth; at higher added concentrations, wild-type BAF completely blocked chromatin decondensation and nuclear growth. Mutants fell into four classes, including one that defines a novel functional surface on the BAF dimer. Our results suggest that BAF, unregulated, potently compresses chromatin structure, and that BAF interactions with both DNA and LEM proteins are critical for membrane recruitment and chromatin decondensation during nuclear assembly.
Segura-Totten
Miriam
M
Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Kowalski
Amy K
AK
Craigie
Robert
R
Wilson
Katherine L
KL
D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D002478:Cells, Cultured; D002843:Chromatin / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000032:analysis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D019281:Dimerization; D005057:Eukaryotic Cells / Q000378:metabolism* / Q000648:ultrastructure; D005260:Female; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008854:Microscopy, Electron; D016297:Mutagenesis, Site-Directed; D009685:Nuclear Envelope / Q000378:metabolism* / Q000648:ultrastructure; D009687:Nuclear Proteins; D009865:Oocytes; D010641:Phenotype; D017354:Point Mutation / Q000502:physiology; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D013946:Thymopoietins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
C501959:BANF1 protein, human; D002843:Chromatin; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D013946:Thymopoietins; C092710:emerin; C093413:lamina-associated polypeptide 2