Modifications of both selectivity factor and upstream binding factor contribute to poliovirus-mediated inhibition of RNA polymerase I transcription.
Soon after infection, poliovirus (PV) shuts off host-cell transcription, which is catalysed by all three cellular RNA polymerases. rRNA constitutes more than 50 % of all cellular RNA and is transcribed from rDNA by RNA polymerase I (pol I). Here, evidence has been provided suggesting that both pol I transcription factors, SL-1 (selectivity factor) and UBF (upstream binding factor), are modified and inactivated in PV-infected cells. The viral protease 3C(pro) appeared to cleave the TATA-binding protein-associated factor 110 (TAF(110)), a subunit of the SL-1 complex, into four fragments in vitro. In vitro protease-cleavage assays using various mutants of TAF(110) and purified 3C(pro) indicated that the Q(265)G(266) and Q(805)G(806) sites were cleaved by 3C(pro). Both SL-1 and UBF were depleted in PV-infected cells and their disappearance correlated with pol I transcription inhibition. rRNA synthesis from a template containing a human pol I promoter demonstrated that both SL-1 and UBF were necessary to restore pol I transcription fully in PV-infected cell extracts. These results suggested that both SL-1 and UBF are transcriptionally inactivated in PV-infected HeLa cells.
Banerjee
Rajeev
R
Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, UCLA School of Medicine, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA.
Weidman
Mary K
MK
Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, UCLA School of Medicine, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA.
Navarro
Sonia
S
Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
Comai
Lucio
L
Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
Dasgupta
Asim
A
Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, UCLA School of Medicine, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA.
D000086042:3C Viral Proteases; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004275:DNA, Ribosomal / Q000235:genetics*; D005973:Glutamine; D005998:Glycine; D006367:HeLa Cells; D006801:Humans; D035463:Pol1 Transcription Initiation Complex Proteins / Q000378:metabolism*; D017955:Poliovirus / Q000201:enzymology*; D011401:Promoter Regions, Genetic; D012318:RNA Polymerase I / Q000037:antagonists & inhibitors* / Q000235:genetics; D035381:TATA-Binding Protein Associated Factors / Q000737:chemistry / Q000378:metabolism; D035362:Transcription Factor TFIID / Q000737:chemistry / Q000378:metabolism; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000378:metabolism
D004275:DNA, Ribosomal; D035463:Pol1 Transcription Initiation Complex Proteins; C486319:TAF1C protein, human; D035381:TATA-Binding Protein Associated Factors; D035362:Transcription Factor TFIID; D014764:Viral Proteins; C063844:transcription factor UBF; C063660:transcription initiation factor TIF-IB; D005973:Glutamine; D012318:RNA Polymerase I; D003546:Cysteine Endopeptidases; D000086042:3C Viral Proteases; D005998:Glycine