Using atomic force microscopy (AFM), the dynamic process of the in vitro nucleosome reconstitution followed by slow dilution from high salt to low salt was visualized. Data showed that the histone octamers were dissoc...Using atomic force microscopy (AFM), the dynamic process of the in vitro nucleosome reconstitution followed by slow dilution from high salt to low salt was visualized. Data showed that the histone octamers were dissociated from DNA at 1M NaCl. When the salt concentration was slowly reduced to 650 mMand 300 mM, the core histones bound to the naked DNA gradually. Once the salt concentration was reduced to 50 mM the classic 'beads-on-a-string' structure was clearly visualized. Furthermore, using the technique of the in vitro reconstitution ofnucleosome,the mono- and di- nucleosomes were assembled in vitro with both HS2core (-10681 to -10970 bp) and NCR2 (-372to -194 bp) DNA sequences in the 5'flanking sequence of human b-globin gene. Data revealed that HMG 1/2 and HMG 14/17 proteins binding to both DNA sequences are changeable following the assembly and disassembly of nucleosomes. We suggest that the changeable binding patterns of HMG 14/17 and HMG1/2 proteins with these regulatory elements may be critical in the process of nucleosome assembly, recruitment of chromatin-modifying activities, and the regulation of human b-globin gene expression.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant No.39893320 and 39870378)the Foundation of the Chinese Academy of Sciences(Grant No.Kj982-j1-618).
文摘Using atomic force microscopy (AFM), the dynamic process of the in vitro nucleosome reconstitution followed by slow dilution from high salt to low salt was visualized. Data showed that the histone octamers were dissociated from DNA at 1M NaCl. When the salt concentration was slowly reduced to 650 mMand 300 mM, the core histones bound to the naked DNA gradually. Once the salt concentration was reduced to 50 mM the classic 'beads-on-a-string' structure was clearly visualized. Furthermore, using the technique of the in vitro reconstitution ofnucleosome,the mono- and di- nucleosomes were assembled in vitro with both HS2core (-10681 to -10970 bp) and NCR2 (-372to -194 bp) DNA sequences in the 5'flanking sequence of human b-globin gene. Data revealed that HMG 1/2 and HMG 14/17 proteins binding to both DNA sequences are changeable following the assembly and disassembly of nucleosomes. We suggest that the changeable binding patterns of HMG 14/17 and HMG1/2 proteins with these regulatory elements may be critical in the process of nucleosome assembly, recruitment of chromatin-modifying activities, and the regulation of human b-globin gene expression.
