Histone variant H2A.Z-containing nucleosomes are incorporated at most eukaryotic promoters. This incorporation is mediated by the conserved SWR1 complex, which replaces histone H2A in canonical nucleosomes with H2A.Z in an ATP-dependent manner. Here, we show that promoter-proximal nucleosomes are highly heterogeneous for H2A.Z in Saccharomyces cerevisiae, with substantial representation of nucleosomes containing one, two, or zero H2A.Z molecules. SWR1-catalyzed H2A.Z replacement in vitro occurs in a stepwise and unidirectional fashion, one H2A.Z-H2B dimer at a time, producing heterotypic nucleosomes as intermediates and homotypic H2A.Z nucleosomes as end products. The ATPase activity of SWR1 is specifically stimulated by H2A-containing nucleosomes without ensuing histone H2A eviction. Remarkably, further addition of free H2A.Z-H2B dimer leads to hyperstimulation of ATPase activity, eviction of nucleosomal H2A-H2B, and deposition of H2A.Z-H2B. These results suggest that the combination of H2A-containing nucleosome and free H2A.Z-H2B dimer acting as both effector and substrate for SWR1 governs the specificity and outcome of the replacement reaction.
Histone variant H2A.Z - containing nucleosomes are incorporated at most eukaryotic promoters . This incorporation is mediated by the conserved SWR1 complex , which replaces histone H2A in canonical nucleosomes with H2A.Z in an ATP - dependent manner . Here , we show that promoter - proximal nucleosomes are highly heterogeneous for H2A.Z in Saccharomyces cerevisiae , with substantial representation of nucleosomes containing one , two , or zero H2A.Z molecules . SWR1-catalyzed H2A.Z replacement in vitro occurs in a stepwise and unidirectional fashion , one H2A.Z - H2B dimer at a time , producing heterotypic nucleosomes as intermediates and homotypic H2A.Z nucleosomes as end products . The ATPase activity of SWR1 is specifically stimulated by H2A - containing nucleosomes without ensuing histone H2A eviction . Remarkably , further addition of free H2A.Z - H2B dimer leads to hyperstimulation of ATPase activity , eviction of nucleosomal H2A - H2B , and deposition of H2A.Z - H2B. These results suggest that the combination of H2A - containing nucleosome and free H2A.Z - H2B dimer acting as both effector and substrate for SWR1 governs the specificity and outcome of the replacement reaction .
Which protein mediates the replacement of H2A by H2A.Z in the yeast Saccharomyces cerevisiae?
Which protein mediates the replacement of H2A by H2A.Z in the yeast Saccharomyces cerevisiae ?
SWR1
SWR1