Retrovirology, 2014, 01, 0─0

NUCKS1, a novel Tat coactivator, plays a crucial role in HIV-1 replication by increasing Tat-mediated viral tranion on the HIV-1 LTR promoter

Hye-Young Kim, B Choi, S Kim, Tg Roh, J Park, C Yoon

Abstract

Background
Human immunodeficiency virus-1 (HIV-1) Tat protein plays an essential role in HIV gene tranion from the HIV-1 long terminal repeat (LTR) and replication. Tranional activity of Tat is modulated by several host factors, but the mechanism responsible for Tat regulation by host factors is not understood fully.
Results
Using a yeast two-hybrid screening system, we identified Nuclear ubiquitous casein and cyclin-dependent kinase substrate 1 (NUCKS1) as a novel Tat-interacting partner. Here, we report its function as a positive regulator of Tat. In a coimmunoprecipitation assay, HIV-1 Tat interacted sufficiently with both endogenous and ectopically expressed NUCKS1.
In a reporter assay, ectopic expression of NUCKS1 significantly increased Tat-mediated tranion of the HIV-1 LTR, whereas knockdown of NUCKS1 by small interfering RNA diminished Tat-mediated tranion of the HIV-1 LTR. We also investigated which mechanism contributes to NUCKS1-mediated Tat activation. In a chromatin immunoprecipitation assay (ChIP), knockdown of NUCKS1 interrupted the accumulation of Tat in the transactivation-responsive (TAR) region on the LTR, which then led to suppression of viral replication.
However, NUCKS1 expression did not increase Tat nuclear localization and interaction with Cyclin T1. Interestingly, the NUCKS1 expression level was lower in latently HIV-1-infected cells than in uninfected parent cells. Besides, expression level of NUCKS1 was markedly induced, which then facilitated HIV-1 reactivation in latently infected cells.
Conclusion
Taken together, our data demonstrate clearly that NUCKS1 is a novel Tat coactivator that is required for Tat-mediated HIV-1 tranion and replication, and that it may contribute to HIV-1 reactivation in latently HIV-1 infected cells.

• ISBN or ISSN: 1742-4690

• 본 연구는 질병관리본부 연구개발과제(과제번호 2013-NG51002-00) 연구비를 지원받아 수행되었습니다.
• This research was supported by a fund(code 2013-NG51002-00) by Research of Korea Centers for Disease Control and Prevention.