RESUMEN
Dynamics of +1 and -1 nucleosomes near TSS of yeast chromosome 2 were analyzed by using second-order information entropy and density functional theory method. Second-order information entropy can measure the interaction intensity between nucleosome sequences and nucleosome histones based on the intensity of base association. In addition, density functional theory method can be used to obtain the global interaction intensity between nucleosome sequences and nucleosome histones based on energy state size and active or non-active state of binucleoside pairs. Our results showed asymmetry of interaction intensity on both sides of the nucleosome central site, and that +1 nucleosomes tend to move toward the 5'-end and -1 nucleosomes tend to move toward the 3'-end. Under the dynamic balance of nucleosome movement, in roder to shut down gene transcription, +1 and -1 nucleosomes will cover TSS. If the dynamic balance is destroyed, +1 and -1 nucleosomes stay away from each other to expose TSS to restart gene transcription. The movement trend of +1 and -1 nucleosomes coincides with the biological mechanism of gene transcription and non-transcription, and the nucleosome sequences contain the dynamic information of nucleosome movement, which provides effective technical support for the study of gene transcription regulation mechanism.
Asunto(s)
Entropía , Nucleosomas/metabolismo , Ensamble y Desensamble de Cromatina , Teoría Funcional de la Densidad , Regulación de la Expresión Génica , Transcripción GenéticaRESUMEN
Nucleosomes are the fundamental building blocks of chromatin that regulate DNA access and are composed of histone octamers. ATP-dependent chromatin remodelers like ISW2 regulate chromatin access by translationally moving nucleosomes to different DNA regions. We find that histone octamers are more pliable than previously assumed and distorted by ISW2 early in remodeling before DNA enters nucleosomes and the ATPase motor moves processively on nucleosomal DNA. Uncoupling the ATPase activity of ISW2 from nucleosome movement with deletion of the SANT domain from the C terminus of the Isw2 catalytic subunit traps remodeling intermediates in which the histone octamer structure is changed. We find restricting histone movement by chemical crosslinking also traps remodeling intermediates resembling those seen early in ISW2 remodeling with loss of the SANT domain. Other evidence shows histone octamers are intrinsically prone to changing their conformation and can be distorted merely by H3-H4 tetramer disulfide crosslinking.