ZBRK1 represses HIV-1 LTR-mediated transcription.

The identification of cellular proteins that interact with the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) provides a basic understanding of HIV-1 gene expression, which is the major determinant regulating virus replication. We show that ZBRK1 negatively regulates the HIV-1 LTR. Ectopic expression of ZBRK1 represses transcriptional activity of the HIV-1 LTR, whereas the depletion of endogenous ZBRK1 leads to activation of the HIV-1 LTR. The repressor activity of ZBRK1 is required for TRIM28 binding. Furthermore, ZBRK1 is bound to the HIV-1 LTR in vivo. These results indicate that ZBRK1 could be involved in a potent intrinsic antiretroviral defense.