Abstract
Covalent modification of histones is important in regulating chromatin dynamics and transcription. One example of such modification is ubiquitination, which mainly occurs on histones H2A and H2B. Although recent studies have uncovered the enzymes involved in histone H2B ubiquitination and a 'cross-talk' between H2B ubiquitination and histone methylation, the responsible enzymes and the functions of H2A ubiquitination are unknown. Here we report the purification and functional characterization of an E3 ubiquitin ligase complex that is specific for histone H2A. The complex, termed hPRC1L (human Polycomb repressive complex 1-like), is composed of several Polycomb-group proteins including Ring1, Ring2, Bmi1 and HPH2. hPRC1L monoubiquitinates nucleosomal histone H2A at lysine 119. Reducing the expression of Ring2 results in a dramatic decrease in the level of ubiquitinated H2A in HeLa cells. Chromatin immunoprecipitation analysis demonstrated colocalization of dRing with ubiquitinated H2A at the PRE and promoter regions of the Drosophila Ubx gene in wing imaginal discs. Removal of dRing in SL2 tissue culture cells by RNA interference resulted in loss of H2A ubiquitination concomitant with derepression of Ubx. Thus, our studies identify the H2A ubiquitin ligase, and link H2A ubiquitination to Polycomb silencing.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Animals
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Catalytic Domain
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Cell Line
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DNA-Binding Proteins / chemistry
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / isolation & purification
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DNA-Binding Proteins / metabolism
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Drosophila Proteins / genetics
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Drosophila melanogaster / genetics
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Gene Silencing*
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HeLa Cells
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Histones / metabolism*
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Homeodomain Proteins / genetics
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Humans
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Molecular Sequence Data
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Multiprotein Complexes
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Nuclear Proteins / genetics
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Nuclear Proteins / isolation & purification
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Nuclear Proteins / metabolism
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Nucleosomes / chemistry
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Nucleosomes / metabolism
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Polycomb Repressive Complex 1
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Polycomb Repressive Complex 2
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Polycomb-Group Proteins
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Promoter Regions, Genetic / genetics
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Protein Subunits / chemistry
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Protein Subunits / genetics
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Protein Subunits / isolation & purification
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Protein Subunits / metabolism
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / isolation & purification
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Proto-Oncogene Proteins / metabolism
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Repressor Proteins / chemistry
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Repressor Proteins / genetics
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Repressor Proteins / isolation & purification
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Repressor Proteins / metabolism*
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Response Elements / genetics
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Transcription Factors / genetics
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Transcription Factors / isolation & purification
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Transcription Factors / metabolism
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Ubiquitin / metabolism*
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Ubiquitin-Protein Ligases / chemistry*
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Ubiquitin-Protein Ligases / genetics
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Ubiquitin-Protein Ligases / isolation & purification
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Ubiquitin-Protein Ligases / metabolism*
Substances
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BMI1 protein, human
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DNA-Binding Proteins
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Drosophila Proteins
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Histones
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Homeodomain Proteins
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Multiprotein Complexes
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Nuclear Proteins
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Nucleosomes
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PHC2 protein, human
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Polycomb-Group Proteins
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Protein Subunits
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Proto-Oncogene Proteins
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Repressor Proteins
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Transcription Factors
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Ubiquitin
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Ubx protein, Drosophila
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Polycomb Repressive Complex 2
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Polycomb Repressive Complex 1
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RING1 protein, human
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Ubiquitin-Protein Ligases