title: Sp100A promotes chromatin decondensation at a cytomegalovirus-promoter-regulated transcription site.
abstract: Promyelocytic leukemia nuclear bodies (PML-NBs)/nuclear domain 10s (ND10s) are nuclear structures that contain many transcriptional and chromatin regulatory factors. One of these, Sp100, is expressed from a single-copy gene and spliced into four isoforms (A, B, C, and HMG), which differentially regulate transcription. Here we evaluate Sp100 function in single cells using an inducible cytomegalovirus-promoter-regulated transgene, visualized as a chromatinized transcription site. Sp100A is the isoform most strongly recruited to the transgene array, and it significantly increases chromatin decondensation. However, Sp100A cannot overcome Daxx- and α-thalassemia mental retardation, X-linked (ATRX)-mediated transcriptional repression, which indicates that PML-NB/ND10 factors function within a regulatory hierarchy. Sp100A increases and Sp100B, which contains a SAND domain, decreases acetyl-lysine regulatory factor levels at activated sites, suggesting that Sp100 isoforms differentially regulate transcription by modulating lysine acetylation. In contrast to Daxx, ATRX, and PML, Sp100 is recruited to activated arrays in cells expressing the herpes simplex virus type 1 E3 ubiquitin ligase, ICP0, which degrades all Sp100 isoforms except unsumoylated Sp100A. The recruitment Sp100A(K297R), which cannot be sumoylated, further suggests that sumoylation plays an important role in regulating Sp100 isoform levels at transcription sites. This study provides insight into the ways in which viruses may modulate Sp100 to promote their replication cycles.
authors.affiliation: Molecular and Cellular Oncogenesis Program, Wistar Institute, Philadelphia, PA 19104, USA.
authors.forename: Alyshia
authors.initials: A
authors.lastname: Newhart
authors.forename: Dmitri G
authors.initials: DG
authors.lastname: Negorev
authors.forename: Ilona U
authors.initials: IU
authors.lastname: Rafalska-Metcalf
authors.forename: Tian
authors.initials: T
authors.lastname: Yang
authors.forename: Gerd G
authors.initials: GG
authors.lastname: Maul
authors.forename: Susan M
authors.initials: SM
authors.lastname: Janicki
mesh_terms: D000107:Acetylation; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D034961:Antigens, Nuclear / Q000378:metabolism*; D001324:Autoantigens / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly; D056970:Co-Repressor Proteins; D003587:Cytomegalovirus / Q000502:physiology*; D004265:DNA Helicases / Q000378:metabolism; D044127:Epigenesis, Genetic; D006367:HeLa Cells; D006801:Humans; D018832:Molecular Chaperones; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D000071156:Promyelocytic Leukemia Protein; D020033:Protein Isoforms / Q000378:metabolism; D021381:Protein Transport; D059748:Proteolysis; D058207:Sumoylation; D014157:Transcription Factors / Q000378:metabolism; D024363:Transcription Initiation Site; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D017735:Virus Latency; D000075924:X-linked Nuclear Protein
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D034961:Antigens, Nuclear; D001324:Autoantigens; C094297:CALCOCO2 protein, human; D056970:Co-Repressor Proteins; C106985:DAXX protein, human; D018832:Molecular Chaperones; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D020033:Protein Isoforms; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C066642:SP100 protein, human; C070576:PML protein, human; D004265:DNA Helicases; C092332:ATRX protein, human; D000075924:X-linked Nuclear Protein