Burgio Giosalba, La Rocca Gaspare, Sala Anna, Arancio Walter, Di Gesù Dario, Collesano Marianna, Sperling Adam S, Armstrong Jennifer A, van Heeringen Simon J, Logie Colin, Tamkun John W, Corona Davide F V
Dipartimento di Scienze Biochimiche, Universita' degli Studi di Palermo, Palermo, Italy.
PLoS Genet. 2008 Jun 6;4(6):e1000089. doi: 10.1371/journal.pgen.1000089.
Nucleosome remodeling and covalent modifications of histones play fundamental roles in chromatin structure and function. However, much remains to be learned about how the action of ATP-dependent chromatin remodeling factors and histone-modifying enzymes is coordinated to modulate chromatin organization and transcription. The evolutionarily conserved ATP-dependent chromatin-remodeling factor ISWI plays essential roles in chromosome organization, DNA replication, and transcription regulation. To gain insight into regulation and mechanism of action of ISWI, we conducted an unbiased genetic screen to identify factors with which it interacts in vivo. We found that ISWI interacts with a network of factors that escaped detection in previous biochemical analyses, including the Sin3A gene. The Sin3A protein and the histone deacetylase Rpd3 are part of a conserved histone deacetylase complex involved in transcriptional repression. ISWI and the Sin3A/Rpd3 complex co-localize at specific chromosome domains. Loss of ISWI activity causes a reduction in the binding of the Sin3A/Rpd3 complex to chromatin. Biochemical analysis showed that the ISWI physically interacts with the histone deacetylase activity of the Sin3A/Rpd3 complex. Consistent with these findings, the acetylation of histone H4 is altered when ISWI activity is perturbed in vivo. These findings suggest that ISWI associates with the Sin3A/Rpd3 complex to support its function in vivo.
核小体重塑和组蛋白的共价修饰在染色质结构和功能中发挥着重要作用。然而，关于ATP依赖的染色质重塑因子和组蛋白修饰酶的作用是如何协调以调节染色质组织和转录，仍有许多有待了解之处。进化上保守的ATP依赖的染色质重塑因子ISWI在染色体组织、DNA复制和转录调控中发挥着重要作用。为了深入了解ISWI的调控和作用机制，我们进行了一项无偏向性的遗传筛选，以鉴定其在体内相互作用的因子。我们发现ISWI与一个在先前生化分析中未被检测到的因子网络相互作用，包括Sin3A基因。Sin3A蛋白和组蛋白去乙酰化酶Rpd3是参与转录抑制的保守组蛋白去乙酰化酶复合物的一部分。ISWI和Sin3A/Rpd3复合物在特定的染色体结构域共定位。ISWI活性的丧失导致Sin3A/Rpd3复合物与染色质的结合减少。生化分析表明，ISWI与Sin3A/Rpd3复合物的组蛋白去乙酰化酶活性发生物理相互作用。与这些发现一致，当体内ISWI活性受到干扰时，组蛋白H4的乙酰化会发生改变。这些发现表明，ISWI与Sin3A/Rpd3复合物相关联，以支持其在体内的功能。
