title: Zhangfei is a potent and specific inhibitor of the host cell factor-binding transcription factor Luman.
abstract: Host cell factor (HCF) was initially discovered as a cellular co-factor required for the activation of herpes simplex virus immediate early gene expression by the virion associated transactivator VP16. HCF also participates in a variety of cellular processes, although the mechanism of its action is not known. VP16 binds to HCF through a 4-amino acid motif (EHAY), which closely resembles the HCF binding domain of two cellular basic leucine-zipper proteins, Luman and Zhangfei. Luman is a powerful transcription factor that, in transient expression assays, activates promoters containing cAMP or unfolded protein response elements (UPRE). In contrast, Zhangfei neither binds consensus recognition elements for basic leucine-zipper proteins nor does it activate promoters containing them. Here we show that Zhangfei suppresses the ability of Luman to activate transcription. HCF appeared to be required for efficient suppression. A mutant of Zhangfei, which was unable to bind HCF, was impaired in its ability to suppress Luman. Zhangfei did not suppress ATF6, a transcription factor closely related to Luman but that does not bind HCF, unless the HCF binding motif of Luman was grafted onto it. Zhangfei inhibited the HCF-dependent activation of a UPRE-containing promoter by a Gal4-Luman fusion protein but was unable to inhibit the HCF-independent activation by Gal4-Luman of a promoter that contained Gal4 binding motifs. Binding of HCF by Zhangfei was required for the co-localization of Luman and Zhangfei to nuclear domains, suggesting that HCF might target the proteins to a common location.
authors.affiliation: Department of Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada. vikram.misra@usask.ca <vikram.misra@usask.ca>
authors.forename: Vikram
authors.initials: V
authors.lastname: Misra
authors.forename: Noreen
authors.initials: N
authors.lastname: Rapin
authors.forename: Oksana
authors.initials: O
authors.lastname: Akhova
authors.forename: Matthew
authors.initials: M
authors.lastname: Bainbridge
authors.forename: Paul
authors.initials: P
authors.lastname: Korchinski
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005822:Genetic Vectors; D017405:Herpes Simplex Virus Protein Vmw65 / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D007930:Leucine / Q000737:chemistry; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D000071156:Promyelocytic Leukemia Protein; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D020218:Response Elements; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection; D025521:Tumor Suppressor Proteins
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; C107941:CREB3 protein, human; C411104:CREBZF protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D017405:Herpes Simplex Virus Protein Vmw65; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C070576:PML protein, human; D012313:RNA; D000242:Cyclic AMP; D007930:Leucine