Nucleosome recognition and spacing by chromatin remodelling factor ISW1a

Nucleosomes are actively positioned along DNA by ATP-dependent, chromatin remodelling factors. A structural model for the ISW1a chromatin remodelling factor from Saccharomyces cerevisiae in complex with a dinucleosome substrate was constructed from the X-ray structures of ISW1a (ΔATPase) with and without DNA bound, two different cryo-EM (cryo-electron microscopy) structures of ISW1a (ΔATPase) bound to a nucleosome, and site-directed photo-cross-linking analyses in solution. The X-ray structure of ISW1a (ΔATPase) with DNA bound suggests that DNA sequence may be involved in nucleosome recognition and thereby specificity of promoter interaction. The model suggests how the highly ordered nucleosome arrays observed by mapping nucleosomes in genes and their promoter regions could be generated by a chromatin remodelling factor.     

Elongator复合物:一种新的参与转录延伸的组蛋白乙酰转移酶

由6个亚基组成的Elongator复合物是RNA聚合酶Ⅱ（RNA polymeraseⅡ．RNAPⅡ）全酶的一个重要组成部分,它可以与高度磷酸化的RNAPⅡ相结合,其Elp3亚基具有组蛋白乙酰转移酶（histone acetyltransferase,HAT）活性,在以染色质为模板的转录延伸中发挥重要作用。Elongator是目前发现的第一个参与转录延伸的HAT复合物。