Specific acetylation of chromosomal protein HMG-17 by PCAF alters its interaction with nucleosomes

Mol Cell Biol. 1999 May;19(5):3466-73. doi: 10.1128/mcb.19.5.3466.

Abstract

Nonhistone chromosomal proteins HMG-14 and HMG-17 are closely related nucleosomal binding proteins that unfold the higher-order chromatin structure, thereby enhancing the transcription and replication potential of chromatin. Here we report that PCAF, a transcription coactivator with intrinsic histone acetyltransferase activity, specifically acetylates HMG-17 but not HMG-14. Using mass spectrum sequence analysis, we identified the lysine at position 2 as the predominant site acetylated by PCAF. Lysine 2 is a prominent acetylation site in vivo, suggesting that this PCAF-mediated acetylation is physiologically relevant. Experiments with HMG-17 deletion mutants and competition studies with various protein fragments indicate that the specific acetylation of HMG-17 is not determined solely by the primary sequence near the acetylation site. By equilibrium dialysis we demonstrated that acetylation reduces the affinity of HMG-17 to nucleosome cores. In addition, we found that the binding of HMG-14 and HMG-17 to nucleosome cores inhibits the PCAF-mediated acetylation of histone H3. Thus, the presence of HMG-14 and HMG-17 affects the ability of PCAF to acetylate chromatin, while the acetylation of HMG-17 reduces its binding affinity to chromatin. Conceivably, in HMG-17-containing chromatin, acetylation of HMG-17 precedes the acetylation of histones.

MeSH terms

  • Acetylation
  • Acetyltransferases / metabolism*
  • Animals
  • Cattle
  • Chromatin / metabolism
  • High Mobility Group Proteins / chemistry
  • High Mobility Group Proteins / metabolism*
  • Histone Acetyltransferases
  • Histones / metabolism
  • Humans
  • Lysine / metabolism
  • Mass Spectrometry
  • Nucleosomes / metabolism*
  • Peptide Fragments / pharmacology
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae Proteins*
  • Transcription Factors / metabolism

Substances

  • Chromatin
  • High Mobility Group Proteins
  • Histones
  • Nucleosomes
  • Peptide Fragments
  • Recombinant Proteins
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • Acetyltransferases
  • Histone Acetyltransferases
  • Lysine