INI1/SMARCB1 Rpt1 domain mimics TAR RNA in binding to integrase to facilitate HIV-1 replication
Updesh Dixit, Savita Bhutoria, Xuhong Wu, Liming Qiu, Menachem Spira, Sheeba Mathew, Richard Harris, Lucas J. Adams, Sean M. Cahill, Rajiv Pathak, P. Rajesh Kumar, Minh Anh Nguyen, Seetharama A. Acharya, Michael Brenowitz, Steven C. Almo, Xiaoqin Zou, Alasdair C. Steven, David Cowburn, Mark E. Girvin, Ganjam V. Kalpana
Abstract
Abstract INI1/SMARCB1 binds to HIV-1 integrase (IN) through its Rpt1 domain and exhibits multifaceted role in HIV-1 replication. Determining the NMR structure of INI1-Rpt1 and modeling its interaction with the IN-C-terminal domain (IN-CTD) reveal that INI1-Rpt1/IN-CTD interface residues overlap with those required for IN/RNA interaction. Mutational analyses validate our model and indicate that the same IN residues are involved in both INI1 and RNA binding. INI1-Rpt1 and TAR RNA compete with each other for IN binding with similar IC 50 values. INI1-interaction-defective IN mutant viruses are impaired for incorporation of INI1 into virions and for particle morphogenesis. Computational modeling of IN-CTD/TAR complex indicates that the TAR interface phosphates overlap with negatively charged surface residues of INI1-Rpt1 in three-dimensional space, suggesting that INI1-Rpt1 domain structurally mimics TAR. This possible mimicry between INI1-Rpt1 and TAR explains the mechanism by which INI1/SMARCB1 influences HIV-1 late events and suggests additional strategies to inhibit HIV-1 replication.