title: Host protein Ku70 binds and protects HIV-1 integrase from proteasomal degradation and is required for HIV replication.
abstract: HIV-1 integrase (IN) is a key viral enzymatic protein acting in several viral replication steps, including integration. IN has been shown to be an unstable protein degraded by the N-end rule pathway through the host ubiquitin-proteasome machinery. However, it is still not fully understood how this viral protein is protected from the host ubiquitin-proteasome system within cells during HIV replication. In the present study, we provide evidence that the host protein Ku70 interacts with HIV-1 IN and protects it from the Lys(48)-linked polyubiquitination proteasomal pathway. Moreover, Ku70 is able to down-regulate the overall protein polyubiquitination level within the host cells and to specifically deubiquitinate IN through their interaction. Mutagenic studies revealed that the C terminus of IN (residues 230-288) is required for IN binding to the N-terminal part of Ku70 (Ku70(1-430)), and their interaction is independent of Ku70/80 heterodimerization. Finally, knockdown of Ku70 expression in both virus-producing and target CD4(+) T cells significantly disrupted HIV-1 replication and rendered two-long terminal repeat circles and integration undetectable, indicating that Ku70 is required for both the early and the late stages of the HIV-1 life cycle. Interestingly, Ku70 was incorporated into the progeny virus in an IN-dependent way. We proposed that Ku70 may interact with IN during viral assembly and accompany HIV-1 IN upon entry into the new target cells, acting to 1) protect IN from the host defense system and 2) assist IN integration activity. Overall, this report provides another example of how HIV-1 hijacks host cellular machinery to protect the virus itself and to facilitate its replication.
authors: Laboratory of Molecular Human Retrovirology, Department of Medical Microbiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada.
authors: Yingfeng
authors: Y
authors: Zheng
authors: Zhujun
authors: Z
authors: Ao
authors: Binchen
authors: B
authors: Wang
authors: Kallesh Danappa
authors: KD
authors: Jayappa
authors: Xiaojian
authors: X
authors: Yao
mesh_terms: D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism*; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism / Q000821:virology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D019427:HIV Integrase / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D000072200:Ku Autoantigen; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D054875:Ubiquitination; D019065:Virus Assembly / Q000502:physiology*
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D019427:HIV Integrase; D046988:Proteasome Endopeptidase Complex; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen