Mutations in the heterochromatin protein 1 (HP1) hinge domain affect HP1 protein interactions and chromosomal distribution

Ramakrishna Badugu, Youngdong Yoo, Prim B Singh, Rebecca Kellum

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Heterochromatin Protein 1 (HP1) is a conserved component of the highly compact chromatin found at centromeres and telomeres. A conserved feature of the protein is multiple phosphorylation. Hyper-phosphorylation of HP1 accompanies the assembly of cytologically distinct heterochromatin during early embryogenesis. Hypo-phosphorylated HP1 is associated with the DNA-binding activities of the origin recognition complex (ORC) and an HMG-like HP1/ORC-Associated Protein (HOAP). Perturbations in HP1 localization in pericentric and telomeric heterochromatin in mutants for Drosophila ORC2 and HOAP, respectively, indicate roles for these HP1 phosphoisoforms in heterochromatin assembly also. To elucidate the roles of hypo- and hyper-phosphophorylated HP1 in heterochromatin assembly, we have mutated consensus Protein Kinase-A phosphorylation sites in the HP1 hinge domain and examined the mutant proteins for distinct in vitro and in vivo activities. Mutations designed to mimic hyper-phosphorylation render the protein incapable of binding HOAP and the DmORC1 subunit but confer enhanced homo-dimerization and lysine 9-methylated histone H3-binding to the protein. Mutations rendering the protein unphosphorylatable, by contrast, do not affect homo-dimerization or binding to lysine 9-di-methylated histone H3, HOAP, or DmORC1 but do confer novel DmORC2-binding activity to the protein. This mutant protein is ectopically localized throughout the chromosomes when overexpressed in vivo in the presence of a full dose of DmORC2. This ectopic targeting is accompanied by ectopic targeting of lysine 9 tri-methylated histone H3. The distinct activities of these mutant proteins could reflect distinct roles for HP1 phosphoisoforms in heterochromatin structure and function.

Original languageEnglish
Pages (from-to)370-84
Number of pages15
JournalChromosoma
Volume113
Issue number7
DOIs
Publication statusPublished - Feb 2005

Fingerprint

Heterochromatin
Mutation
Proteins
Mutant Proteins
Origin Recognition Complex
Phosphorylation
Histones
Lysine
Dimerization
heterochromatin-specific nonhistone chromosomal protein HP-1
Centromere
Telomere
Protein Subunits
Cyclic AMP-Dependent Protein Kinases
Protein Binding
Chromatin
Embryonic Development
Carrier Proteins
Chromosomes
DNA

Keywords

  • Amino Acid Sequence
  • Animals
  • Chromatin
  • Chromosomal Proteins, Non-Histone
  • DNA Methylation
  • DNA-Binding Proteins
  • Dimerization
  • Drosophila Proteins
  • Drosophila melanogaster
  • Histones
  • Lysine
  • Molecular Sequence Data
  • Mutation
  • Origin Recognition Complex
  • Phosphorylation
  • Protein Binding
  • Protein Interaction Mapping
  • Protein Structure, Tertiary
  • Sequence Homology, Amino Acid
  • Journal Article
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

Cite this

Mutations in the heterochromatin protein 1 (HP1) hinge domain affect HP1 protein interactions and chromosomal distribution. / Badugu, Ramakrishna; Yoo, Youngdong; Singh, Prim B; Kellum, Rebecca.

In: Chromosoma, Vol. 113, No. 7, 02.2005, p. 370-84.

Research output: Contribution to journalArticle

Badugu, Ramakrishna ; Yoo, Youngdong ; Singh, Prim B ; Kellum, Rebecca. / Mutations in the heterochromatin protein 1 (HP1) hinge domain affect HP1 protein interactions and chromosomal distribution. In: Chromosoma. 2005 ; Vol. 113, No. 7. pp. 370-84.
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AU - Badugu, Ramakrishna

AU - Yoo, Youngdong

AU - Singh, Prim B

AU - Kellum, Rebecca

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N2 - Heterochromatin Protein 1 (HP1) is a conserved component of the highly compact chromatin found at centromeres and telomeres. A conserved feature of the protein is multiple phosphorylation. Hyper-phosphorylation of HP1 accompanies the assembly of cytologically distinct heterochromatin during early embryogenesis. Hypo-phosphorylated HP1 is associated with the DNA-binding activities of the origin recognition complex (ORC) and an HMG-like HP1/ORC-Associated Protein (HOAP). Perturbations in HP1 localization in pericentric and telomeric heterochromatin in mutants for Drosophila ORC2 and HOAP, respectively, indicate roles for these HP1 phosphoisoforms in heterochromatin assembly also. To elucidate the roles of hypo- and hyper-phosphophorylated HP1 in heterochromatin assembly, we have mutated consensus Protein Kinase-A phosphorylation sites in the HP1 hinge domain and examined the mutant proteins for distinct in vitro and in vivo activities. Mutations designed to mimic hyper-phosphorylation render the protein incapable of binding HOAP and the DmORC1 subunit but confer enhanced homo-dimerization and lysine 9-methylated histone H3-binding to the protein. Mutations rendering the protein unphosphorylatable, by contrast, do not affect homo-dimerization or binding to lysine 9-di-methylated histone H3, HOAP, or DmORC1 but do confer novel DmORC2-binding activity to the protein. This mutant protein is ectopically localized throughout the chromosomes when overexpressed in vivo in the presence of a full dose of DmORC2. This ectopic targeting is accompanied by ectopic targeting of lysine 9 tri-methylated histone H3. The distinct activities of these mutant proteins could reflect distinct roles for HP1 phosphoisoforms in heterochromatin structure and function.

AB - Heterochromatin Protein 1 (HP1) is a conserved component of the highly compact chromatin found at centromeres and telomeres. A conserved feature of the protein is multiple phosphorylation. Hyper-phosphorylation of HP1 accompanies the assembly of cytologically distinct heterochromatin during early embryogenesis. Hypo-phosphorylated HP1 is associated with the DNA-binding activities of the origin recognition complex (ORC) and an HMG-like HP1/ORC-Associated Protein (HOAP). Perturbations in HP1 localization in pericentric and telomeric heterochromatin in mutants for Drosophila ORC2 and HOAP, respectively, indicate roles for these HP1 phosphoisoforms in heterochromatin assembly also. To elucidate the roles of hypo- and hyper-phosphophorylated HP1 in heterochromatin assembly, we have mutated consensus Protein Kinase-A phosphorylation sites in the HP1 hinge domain and examined the mutant proteins for distinct in vitro and in vivo activities. Mutations designed to mimic hyper-phosphorylation render the protein incapable of binding HOAP and the DmORC1 subunit but confer enhanced homo-dimerization and lysine 9-methylated histone H3-binding to the protein. Mutations rendering the protein unphosphorylatable, by contrast, do not affect homo-dimerization or binding to lysine 9-di-methylated histone H3, HOAP, or DmORC1 but do confer novel DmORC2-binding activity to the protein. This mutant protein is ectopically localized throughout the chromosomes when overexpressed in vivo in the presence of a full dose of DmORC2. This ectopic targeting is accompanied by ectopic targeting of lysine 9 tri-methylated histone H3. The distinct activities of these mutant proteins could reflect distinct roles for HP1 phosphoisoforms in heterochromatin structure and function.

KW - Amino Acid Sequence

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KW - Chromatin

KW - Chromosomal Proteins, Non-Histone

KW - DNA Methylation

KW - DNA-Binding Proteins

KW - Dimerization

KW - Drosophila Proteins

KW - Drosophila melanogaster

KW - Histones

KW - Lysine

KW - Molecular Sequence Data

KW - Mutation

KW - Origin Recognition Complex

KW - Phosphorylation

KW - Protein Binding

KW - Protein Interaction Mapping

KW - Protein Structure, Tertiary

KW - Sequence Homology, Amino Acid

KW - Journal Article

KW - Research Support, N.I.H., Extramural

KW - Research Support, U.S. Gov't, P.H.S.

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DO - 10.1007/s00412-004-0324-2

M3 - Article

C2 - 15592864

VL - 113

SP - 370

EP - 384

JO - Chromosoma

JF - Chromosoma

SN - 0009-5915

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ER -