Remodelling of the S3 PA700 proteasome activator gene chromatin structure during thymocyte differentiation.
The proteasome is the major cytosolic protease, composed of a 20S catalytic core that associates with either the 19S (PA700) activator or the 11S (PA28) regulator complex. The 19S complex is thought to promote protein substrate unfolding and subsequent degradation, but precise functions for the individual subunits remain undefined. The chromatin structure and regulation of the S3 (P91A) subunit of the 19S activator was examined as a novel approach towards understanding its role in the complex. DNase I hypersensitivity (HS) analysis of S3 chromatin revealed a ubiquitous DNase I HS site mapping to the promoter region. Examination of the S3 chromatin structure in thymocytes, a dynamic population that undergo substantial proliferation, apoptosis, and differentiation, revealed an additional DNase I HS site mapping to the sixth intron of the genomic sequence. This second site was demonstrated to be associated with CD4(+)CD8(+) double-positive (DP) but not CD4(+) single-positive (SP) thymoma cell lines, and may correlate with a downregulation of S3 message. When a DP thymic cell line was induced to differentiate through retroviral transduction with Notch-1, the second DNase I HS site was dramatically diminished, illustrating that S3 chromatin is developmentally regulated during thymocyte positive selection.
Division of Cell Biology and Immunology, Wellcome Trust Biocentre, University of Dundee, Dundee, DD1 5EH, Scotland. a.n.antoniou@dundee.ac.uk
Antony N
AN
Antoniou
Nel
N
Moore
P Julian
PJ
Dyson
D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D002843:Chromatin / Q000648:ultrastructure*; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000235:genetics*; D003850:Deoxyribonuclease I / Q000737:chemistry; D015536:Down-Regulation; D005260:Female; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008811:Mice, Inbred DBA; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics*; D046988:Proteasome Endopeptidase Complex; D014176:Protein Biosynthesis; D021122:Protein Subunits; D011506:Proteins / Q000235:genetics*; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D013601:T-Lymphocytes / Q000201:enzymology* / Q000648:ultrastructure; D013950:Thymus Gland / Q000166:cytology / Q000201:enzymology* / Q000276:immunology; D014018:Tissue Distribution; D014157:Transcription Factors; D014407:Tumor Cells, Cultured
D002843:Chromatin; D008565:Membrane Proteins; D009097:Multienzyme Complexes; C497762:Notch1 protein, mouse; C085834:PA700 proteasome activator; D021122:Protein Subunits; D011506:Proteins; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D014157:Transcription Factors; D003850:Deoxyribonuclease I; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex