title: Interactions between HIV-1 Vif and human ElonginB-ElonginC are important for CBF-β binding to Vif.
abstract: BACKGROUND
  The HIV-1 accessory factor Vif is necessary for efficient viral infection in non-permissive cells. Vif antagonizes the antiviral activity of human cytidine deaminase APOBEC3 proteins that confer the non-permissive phenotype by tethering them (APOBEC3DE/3F/3G) to the Vif-CBF-β-ElonginB-ElonginC-Cullin5-Rbx (Vif-CBF-β-EloB-EloC-Cul5-Rbx) E3 complex to induce their proteasomal degradation. EloB and EloC were initially reported as positive regulatory subunits of the Elongin (SIII) complex. Thereafter, EloB and EloC were found to be components of Cul-E3 complexes, contributing to proteasomal degradation of specific substrates. CBF-β is a newly identified key regulator of Vif function, and more information is needed to further clarify its regulatory mechanism. Here, we comprehensively investigated the functions of EloB (together with EloC) in the Vif-CBF-β-Cul5 E3 ligase complex.
  
  
  RESULTS
  The results revealed that: (1) EloB (and EloC) positively affected the recruitment of CBF-β to Vif. Both knockdown of endogenous EloB and over-expression of its mutant with a 34-residue deletion in the COOH-terminal tail (EloBΔC34/EBΔC34) impaired the Vif-CBF-β interaction. (2) Introduction of both the Vif SLQ → AAA mutant (VifΔSLQ, which dramatically impairs Vif-EloB-EloC binding) and the Vif PPL → AAA mutant (VifΔPPL, which is thought to reduce Vif-EloB binding) could reduce CBF-β binding. (3) EloB-EloC but not CBF-β could greatly enhance the folding of full-length Vif in Escherichia coli. (4) The over-expression of EloB or the N-terminal ubiquitin-like (UbL) domain of EloB could significantly improve the stability of Vif/VifΔSLQ/VifΔPPL through the region between residues 9 and 14.
  
  
  CONCLUSIONS
  Our results indicate that the Vif interaction with EloB-EloC may contribute to recruitment of CBF-β to Vif, demonstrating that the EloB C-teminus may play a role in improving Vif function and that the over-expression of EloB results in Vif stabilization.
authors.affiliation: National Engineering Laboratory for AIDS Vaccine, College of Life Science, Jilin University, Changchun, Jilin Province, People's Republic of China. weikong@jlu.edu.cn.
authors.forename: Xiaodan
authors.initials: X
authors.lastname: Wang
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Wang
authors.forename: Haihong
authors.initials: H
authors.lastname: Zhang
authors.forename: Mingyu
authors.initials: M
authors.lastname: Lv
authors.forename: Tao
authors.initials: T
authors.lastname: Zuo
authors.forename: Hui
authors.initials: H
authors.lastname: Wu
authors.forename: Jiawen
authors.initials: J
authors.lastname: Wang
authors.forename: Donglai
authors.initials: D
authors.lastname: Liu
authors.forename: Chu
authors.initials: C
authors.lastname: Wang
authors.forename: Jingyao
authors.initials: J
authors.lastname: Zhang
authors.forename: Xu
authors.initials: X
authors.lastname: Li
authors.forename: Jiaxin
authors.initials: J
authors.lastname: Wu
authors.forename: Bin
authors.initials: B
authors.lastname: Yu
authors.forename: Wei
authors.initials: W
authors.lastname: Kong
authors.forename: Xianghui
authors.initials: X
authors.lastname: Yu
mesh_terms: D002460:Cell Line; D050658:Core Binding Factor beta Subunit / Q000378:metabolism*; D000075065:Elongin; D015497:HIV-1 / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D011485:Protein Binding; D025941:Protein Interaction Mapping; D014157:Transcription Factors / Q000378:metabolism*; D054320:vif Gene Products, Human Immunodeficiency Virus / Q000378:metabolism*
chemical_list: D050658:Core Binding Factor beta Subunit; C000616396:ELOB protein, human; C000616395:ELOC protein, human; D000075065:Elongin; D014157:Transcription Factors; D054320:vif Gene Products, Human Immunodeficiency Virus; C514847:vif protein, Human immunodeficiency virus 1