Histone Deposition Proteins: Links between the DNA Replication Machinery and Epigenetic Gene Silencing
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Excerpt
The information encoded in all eukaryotic genomes isorganized into a nucleoprotein complex called chromatin.Chromatin is essential for compacting genomic DNA andplays a primary role in governing the expression status ofgenes. Chromatin is a diverse and dynamic polymer whosecomposition is modulated to build specialized chromosome structures, such as those found at centromeres andtelomeres (for review, see Grewal and Moazed 2003). Thefundamental repeating unit of chromatin is the nucleosome, containing an octamer of histone proteins, two eachof H2A, H2B, H3, and H4, around which 146 bp of DNAwraps 1.7 times. This review will focus on how nucleosomes are assembled by histone chaperones that deposithistones during DNA replication or RNA transcription.We will begin by describing the biophysical propertiesgoverning nucleosome formation and the mechanisms ofde novo nucleosome formation at sites of DNA synthesis.Then, we will discuss the functional overlap between histone chaperones involved in DNA replication-coupled andreplication-independent nucleosome assembly. Finally,we will review recent data demonstrating the role of histone chaperones in the tight temporal coupling of histonedeposition and DNA replication...
