title: Paramyxoviruses SV5 and HPIV2 assemble STAT protein ubiquitin ligase complexes from cellular components.
abstract: Signal transducer and activator of transcription (STAT) proteins are normally long-lived, but infection with certain Paramyxoviruses results in efficient loss of IFN-responsive STAT1 or STAT2. Expression of a virus-encoded protein called "V" is sufficient to mediate the destruction of STAT proteins. STAT degradation is blocked by proteasome inhibitors, strongly implicating the ubiquitin (Ub)-proteasome targeting system. We demonstrate that cellular expression of V proteins from simian virus 5 (SV5) and type II human parainfluenza virus (HPIV2) induces polyubiquitylation of STAT1 and STAT2 targets. In vitro, the V proteins catalyze Ub transfer in an ATP-dependent process that requires both Ub-activating (E1) and Ub-conjugating (E2) activities. Furthermore, SV5 and HPIV2 V-interacting protein partners were isolated by affinity purification from human cells and reveal a complex of associated cellular proteins. This complex includes both STAT1 and STAT2, and the damaged DNA binding protein, DDB1. In addition, a protein related to a family of cellular Ub ligase complex subunits, cullin 4A (Cul4A), associated with the V proteins. The roles of both DDB1 and Cul4A in STAT1 degradation by SV5 infection were analyzed using small interfering RNAs. These findings demonstrate the assembly of a V-dependent degradation complex that includes STAT1, STAT2, DDB1, and Cul4A. In agreement with prior nomenclature on SCF-type cellular E3 enzymes, we refer to this complex as VDC.
authors.affiliation: Immunobiology Center, Mount Sinai School of Medicine, New York, New York 10029, USA.
authors.forename: Christina M
authors.initials: CM
authors.lastname: Ulane
authors.forename: Curt M
authors.initials: CM
authors.lastname: Horvath
mesh_terms: D000936:Antigen-Antibody Complex / Q000378:metabolism; D002478:Cells, Cultured; D044842:Cullin Proteins; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D008025:Ligases / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism; D034741:RNA, Small Interfering / Q000502:physiology; D018108:Respirovirus / Q000502:physiology*; D050794:STAT1 Transcription Factor; D050795:STAT2 Transcription Factor; D015534:Trans-Activators / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases; D014764:Viral Proteins / Q000502:physiology*; D015678:Viral Structural Proteins / Q000502:physiology*
chemical_list: D000936:Antigen-Antibody Complex; C114234:CUL4A protein, human; D044842:Cullin Proteins; C091435:DDB1 protein, human; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050795:STAT2 Transcription Factor; C494084:STAT2 protein, human; D015534:Trans-Activators; C097019:V protein, Simian parainfluenza virus 5; C068854:V protein, human parainfluenza virus type 1; D014764:Viral Proteins; D015678:Viral Structural Proteins; D044767:Ubiquitin-Protein Ligases; D008025:Ligases