General model for gene regulation Chromatin Modifying Chromatin Remodeling RNA polymerase‖l Factors Factors holoenzyme Activators bind to specific DNA sequences DNa is packaged in higher order chromatin structure 2005-10-29 Chaoqun Wu, Fudan University
2005-10-29 Chaoqun Wu, Fudan University Chaoqun Wu, Fudan University 6 General model for gene regulation RNA polymerase II holoenzyme Chromatin Modifying Factors Chromatin Remodeling Factors DNA is packaged in higher order chromatin structure Activators bind to specific DNA sequences
1. Nucleosome Positioning Nucleosome positioning is the phenomenon Where nucleosomes assume specific positions on a dNA molecule This position has two attributes a rotational setting a translational setting Nucleosomes have defined translational and rotational positions 2005-10-29 Chaoqun Wu, Fudan University
2005-10-29 Chaoqun Wu, Fudan University Chaoqun Wu, Fudan University 7 1. Nucleosome Positioning • Nucleosome positioning is the phenomenon where nucleosomes assume specific positions on a DNA molecule • This position has two attributes: – a rotational setting – a translational setting • Nucleosomes have defined translational and rotational positions
a nucleosome can assume one of several different positions along a dNA molecule This is referred to as translational positioning Position Nucleosome DNA Position 2 Position 3 2005-10-29 Chaoqun Wu, Fudan University
2005-10-29 Chaoqun Wu, Fudan University Chaoqun Wu, Fudan University 8 A nucleosome can assume one of several different positions along a DNA molecule This is referred to as translational positioning Nucleosome DNA Position 1 Position 2 Position 3
This causes certain cis-elements to be located in nucleosomes at positions where the trans-acting factors cannot recognize and bind to them There is therefore a requirement to make nucleosomally wrapped dNA of some gene promoters more accessible This is a function performed by the chromatin remodelers 2005-10-29 Chaoqun Wu, Fudan University
2005-10-29 Chaoqun Wu, Fudan University Chaoqun Wu, Fudan University 9 •This causes certain cis-elements to be located in nucleosomes at positions where the trans-acting factors cannot recognize and bind to them • There is therefore a requirement to make nucleosomally wrapped DNA of some gene promoters more accessible • This is a function performed by the chromatin remodelers
2. Supposed remodeling steps Dissociation of h1 Acetylation and partial decondensation of the chromatin >recruitment of select transcriptional activators Which, in turn recruit Chromatin remodelers(染色质重构复合物) Additional histone modification enzymes The order of recruitment is not known 2005-10-29 Chaoqun Wu, Fudan University
2005-10-29 Chaoqun Wu, Fudan University Chaoqun Wu, Fudan University 10 2. Supposed remodeling steps ¾ Dissociation of H1 ¾ Acetylation and partial decondensation of the chromatin ¾recruitment of select transcriptional activators, which, in turn, recruit • Chromatin remodelers(染色质重构复合物) • Additional histone modification enzymes • The order of recruitment is not known