1. H2A.Z Alters the Nucleosome Surface to Promote HP1α-Mediated Chromatin Fiber Folding 
Jun Y. Fan, Danny Rangasamy, Karolin Luger, David J. Tremethick 
Molecular Cell 
Volume 16, Issue 4, Pages (November 2004)
DOI: /j.molcel

2. Figure 1 HP1α Binds to H2A.Z-Containing Nucleosomes In Vivo
(A and B) ChIP experiments were performed in mouse L929 cells utilizing H2A.Z and H2A antibodies (A), and HP1α antibodies (B). As a control, ChIP assays were also performed using mouse IgG antibodies. Bound and unbound proteins (10 μg of total protein per lane) were subjected to Western analysis using antibodies shown.
(C) The DNA from chromatin fragments, obtained by digesting nuclei for 60 min on ice and immunoprecipitated with H2A or H2A.Z antibodies, was purified and subjected to agarose gel electrophoresis.
Molecular Cell  , DOI: ( /j.molcel )

3. Figure 2
HP1α and H2A.Z Function Together to Produce Highly Folded Secondary Chromatin Structures
(A) A schematic diagram showing the folding of model arrays first into compacted secondary structures and then into highly condensed tertiary structures with increasing divalent cation ion concentration mimicking the in vivo compaction process.
(B) Arrays containing the equivalent of 3 μg of DNA were cleaved with micrococcal nuclease in 1 mM CaCl2.
(C–E) Sedimentation coefficient distribution plots of naked DNA with and without HP1α (C). Sedimentation coefficient distribution plots of (D) H2A and (E) H2A.Z-containing arrays, without MgCl2, in the presence and absence of HP1α.
(F) Effect of HP1α and MgCl2 on the average S of control H2A and H2A.Z nucleosomal arrays. Average sedimentation coefficients (Save) were determined from the rate of sedimentation at the boundary midpoint (boundary fraction = 0.5).
(G) Shown is the percentage of control and H2A.Z nucleosomal arrays, in the absence or presence of HP1α (at rHP1 = 1), that remained in the supernatant following a 10 min incubation and a centrifugation step using the same reconstitutes as above. Each data point represents the average and standard deviation of three independent experiments.
Molecular Cell  , DOI: ( /j.molcel )

4. Figure 3
H2A.Z Alters the Acidic Patch, which Promotes Higher Order Folding
(A) The mouse sequence of the essential region of H2A.Z (boxed), compared to H2A, is shown. The two amino acid residues of H2A.Z (Asp and Ser) that subtly extend the acidic patch region are shown in red. The secondary structure elements of this C-terminal region are indicated.
(B) The extended acid patch of H2A.Z was changed back to H2A by mutating the H2A.Z Asp and Ser residues to the equivalently positioned Asn and Lys residues of H2A, respectively (H2A.ZNK). Sedimentation coefficient distribution plots of nucleosomal arrays, with MgCl2, assembled with H2A.ZNK compared to H2A.Z and control H2A arrays are shown.
(C) Sedimentation coefficient distribution plots of H2A-, H2A.Z-, or H2A.ZNK-containing arrays, without MgCl2, in the presence HP1α (at rHP1 = 1). Shown are the percentage of control H2A, H2A.Z, or H2A.ZNK nucleosomal arrays, in the absence (D) or in presence of HP1α (at rHP1 = 1) (E) that remained in the supernatant following a 10 min incubation and a centrifugation step using the same reconstitutes as above. Each data point represents the average and standard deviation of three independent experiments
(F) Sedimentation coefficient distribution plots of control H2A.Z arrays (with and without MgCl2) and H2A.Z arrays containing the globular domain of histone H4 or histone H2B (with MgCl2).
(G) Sedimentation coefficient distribution plots of control H2A.Z arrays (in the presence or absence of HP1α at rHP1 = 1) and H2A.Z arrays containing the globular domain of histone H4 or histone H2B in the presence HP1α (at rHP1 = 1) without MgCl2.
Molecular Cell  , DOI: ( /j.molcel )