Suka Noriyuki, Luo Kunheng, Grunstein Michael
Department of Biological Chemistry, UCLA School of Medicine and the Molecular Biology Institute, Boyer Hall, University of California, Los Angeles, California 90095, USA.
Nat Genet. 2002 Nov;32(3):378-83. doi: 10.1038/ng1017. Epub 2002 Oct 15.
The Sir3 protein helps form telomeric heterochromatin by interacting with hypoacetylated histone H4 lysine 16 (H4-Lys16). The molecular nature of the heterochromatin boundary is still unknown. Here we show that the MYST-like acetyltransferase Sas2p is required for the acetylation (Ac) of H4-Lys16 in euchromatin. In a sas2Delta strain or a phenocopy Lys16Arg mutant, Sir3p spreads from roughly 3 kb to roughly 15 kb, causing hypoacetylation and repression of adjacent chromatin. We also found that disruption of Sir3p binding in a deacetylase-deficient Sir 2Delta strain can be suppressed by sas2Delta. These data indicate that opposing effects of Sir2p and Sas2p on acetylation of H4-Lys16 maintain the boundary at telomeric heterochromatin.
Sir3蛋白通过与低乙酰化的组蛋白H4赖氨酸16（H4-Lys16）相互作用，帮助形成端粒异染色质。异染色质边界的分子本质仍然未知。在此我们表明，类MYST乙酰转移酶Sas2p是常染色质中H4-Lys16乙酰化（Ac）所必需的。在sas2Δ菌株或表型相似的Lys16Arg突变体中，Sir3p从大约3 kb扩展到大约15 kb，导致相邻染色质的低乙酰化和抑制。我们还发现，在脱乙酰酶缺陷的Sir2Δ菌株中，Sir3p结合的破坏可以被sas2Δ抑制。这些数据表明，Sir2p和Sas2p对H4-Lys16乙酰化的相反作用维持了端粒异染色质的边界。
