Identification of a Cellular Protein That Specifically Interacts with the Essential Cysteine Region of the HIV-1 Tat Transactivator

Abstract

The Tat protein of the human immunodeficiency virus (HIV) is a powerful activator of HIV gene expression. Genetic and biochemical evidence suggests that one or more cellular cofactors may be important for Tat activity. We have used two-hybrid interactive cloning in yeast to identify a partial cDNA clone (clone 10) from a human B-lymphoblastoid library that specifically interacts with the N-terminal 31 amino acids of HIV-1 Tat which contains the essential cysteine-rich portion of the Tat activation domain. The encoded protein also binds to purified Tat in vitro. Mutation of single essential cysteine residues in Tat abolishes interaction between Tat and clone 10, suggesting that interaction with the encoded protein is important for Tat activity. We have identified the full-length cDNA for the Tat binding protein and shown that overexpression of the encoded protein, Tip60 (Tat interactive protein, 60 kDa), results in a fourfold augmentation of Tat transactivation of the HIV-1 promoter in transient expression assays without increasing the basal activity of the HIV promoter or activating the heterologous RSV promoter. These data together with the genetic and in vitro binding data support the notion that Tip60 might be a cofactor of Tat involved in the regulation of HIV gene expression.

MOZ and MORF, two large MYSTic HATs in normal and cancer stem cells

“…Independently, elegant genetic analysis in budding yeast identified Sas2 (something about silencing 2) and Sas3 as two homologous regulators of gene silencing (Reifsnyder et al, 1996). Sequence comparison revealed that the three proteins display high sequence similarity within a B300-residue region with TIP60 (HIV Tatinteractive protein of 60 kDa) (Kamine et al, 1996). The homologous region was named the MYST (MOZ, Ybf2/ Sas3, Sas2 and TIP60) domain (Borrow et al, 1996;Reifsnyder et al, 1996).…”

The Bcl-3 oncoprotein acts as a bridging factor between NF-κB/Rel and nuclear co-regulators

“…Novel Bcl-3 interacting proteins were Pirin, Tip60, Jab1, and Bard1 (Table 1). These proteins had previously been shown to interact with nuclear factor I/ CCAAT box transcription factor (NFI/CTF1) (Wendler et al, 1997), HIV-1 Tat (Kamine et al, 1996), c-Jun (Claret et al, 1996 and Brca1 (Wu et al, 1996), respectively.…”

“…They included Tat-interacting protein Tip60; Pirin, a potential co-factor of nuclear factor I; Bard1, known to functionally interact with the tumor suppressor Brca1 and Jab1, which interacts with the transactivation domain of c-Jun (Claret et al, 1996;Kamine et al, 1996;Wendler et al, 1997;Wu et al, 1996). The only common properties of the identi®ed factors is that they are nuclear proteins and associate with gene regulators.…”

Phosphorylation of Tip60 Tyrosine 327 by Abl Kinase Inhibits HAT Activity through Association with FE65

“…Tip60 was characterized as a partner of the human immunodeficiency virus, type 1-encoded transactivator protein Tat [1, 2]. Tip60 was subsequently identified as a member of the MYST family of nuclear histone acetyltransferases (HATs).…”

“…Moreover, Tip60 appears to be involved in a broad variety of cellular functions [5, 6]. The acetylation is a modification by the acetyltransferases that catalyze the transfer of acetyl groups from acetyl coenzyme A to either the amino group of N-terminal amino acids or the έ-amino group of internal lysine residues [1, 2]. …”