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Self-Perpetuating Structural States in Biology, Disease, and Genetics (2002) / Chapter Skim
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Heritable chromatin structure: Mapping “memory” in histones H3 and H4
Pages 78-85

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From page 78...
... 42, 401-4071. To identify potential sites within the chromatin that might act as sources of "memory" for the heritable transmission, we performed a genetic screen to isolate mutant alleles of the histones H3 and H4 genes that would "lock" telomeric marker genes into a silenced state.
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From page 79...
... Hence there appears to be an intimate coordination between silent chromatin assembly and DNA replication. The role of histone modification as a means of "marking" chromatin to perpetuate the molecular memory of an expression state after DNA replication was suggested 25 years ago (21)
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From page 80...
... The mutant histones still required SIR gene function for silencing (data not shown) , indicating that the mutant histone repression was still mediated by silent chromatin.
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From page 81...
... However, it was possible that the histone mutants increased silencing indirectly; for instance, they may have resulted in the misregulation of silencing proteins. Increased dosage of SIRS causes increased silencing at telomeres and can compensate for some mutants that lose telomeric silencing (31~.
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From page 82...
... To prepare a homogeneous, chemically identical population, purified histone H4 was treated with deuterated acetic anhydride, which labeled each unacetylated lysine with a deuterated acetyl moiety (35~. Trypsin efficiently cleaves after lysine or arginine in a peptide; however, acetylation of lysine protects these residues from cleavage (36~.
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From page 83...
... Presented in Fig. 4B are mass spectra of wild-type and selected mutant histone tryptic peptides; the spectra are placed beneath the lysine residue for which they provide acetylation information.
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From page 84...
... For instance, genetic screens designed to identify unlinked neomorphic alleles that could acetylate K12. Alternatively, the histone mutants could be used as a substrate in biochemical assays with histone acetylases and methylases that have been shown to be involved in telomeric silencing (44-46, 59~.
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From page 85...
... van Leeuwen for comments on the manuscript. National Institutes of Health Grant GM43893 and an Ellison Medical Foundation Senior Scholar Award (to D.E.G.)
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Key Terms

  • silent chromatin
  • wild type
  • increased silencing
  • position effect
  • iysine residues

  • amino acid
  • mass spectrometric
  • deuterated acetic
  • sir complex
  • chromatin assembly

  • deuterated acetylation
  • mutant histones
  • mutant histone
  • lysine residues
  • histone mutants

  • telomeric position
  • telomeric chromatin
  • increase telomeric
  • acetic anhydride
  • single amino

  • acid changes
  • supporting information
  • marker genes
  • mass spectra
  • silenced chromatin

  • transcriptional state
  • lysine residue
  • endogenous acetylation
  • chromatin structure
  • tail peptides


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