Negative regulation of Sp1 trans-activation is correlated with the binding of cellular proteins to the amino terminus of the Sp1 trans-activation domain.

The tumor suppressing capacity of the retinoblastoma protein (p110RB) is dependent on interactions made with cellular proteins through its carboxy-terminal domains. How the p110RB amino-terminal region contributes to this activity is unclear, though evidence now indicates it is important for both growth suppression and regulation of the full-length protein. We have used the yeast two-hybrid system to screen for cellular proteins which bind to the first 300 amino acids of p110RB. The only gene isolated from this screen encodes a novel 84-kD nuclear matrix protein that localizes to subnuclear regions associated with RNA processing. This protein, p84, requires a structurally defined domain in the amino terminus of p110RB for binding. Furthermore, both in vivo and in vitro experiments demonstrate that p84 binds preferentially to the functionally active, hypophosphorylated form of p110RB. Thus, the amino terminus of p110RB may function in part to facilitate the binding of growth promoting factors at subnuclear regions actively involved in RNA metabolism.

Download Full-text

Evidence for an Activation Domain at the Amino Terminus of Simian Immunodeficiency Virus Vpx

Journal of Virology ◽

10.1128/jvi.01437-09 ◽

2009 ◽

Vol 84 (3) ◽

pp. 1387-1396 ◽

Cited By ~ 43

Author(s):

Thomas Gramberg ◽

Nicole Sunseri ◽

Nathaniel R. Landau

Keyword(s):

Dendritic Cells ◽

Simian Immunodeficiency Virus ◽

Structural Similarity ◽

Amino Terminus ◽

Type I ◽

Activation Domain ◽

Amino Terminal ◽

Immunodeficiency Virus ◽

Viruslike Particles ◽

Hiv 1

ABSTRACT Vpx and Vpr are related lentiviral accessory proteins that enhance virus replication in macrophages and dendritic cells. Both proteins are packaged into virions and mediate their effects in the target cell through an interaction with an E3 ubiquitin ligase that contains DCAF1 and DDB1. When introduced into primary macrophages and dendritic cells in viruslike particles, Vpx can enhance the efficiency of a subsequent infection. Here, we confirm the ability of Vpx to enhance simian immunodeficiency virus (SIV) and human immunodeficiency virus type 1 (HIV-1) infection of macrophages up to 100-fold by using single-cycle reporter viruses and by pretreatment of the cells with Vpx-containing viruslike particles. Vpx was also active in differentiated THP-1 cells but not in other cell lines. Induction of an antiviral state in macrophages with type I interferon significantly magnified the effect of Vpx on HIV-1 infection, suggesting that Vpx helps the virus to overcome an inducible intracellular restriction. Quantitative PCR quantitation of SIV and HIV-1 reverse transcripts in newly infected macrophages showed that the block was at an early step in reverse transcription. In spite of its structural similarity, Vpr was inactive. This difference allowed us to map the functional domains of Vpx with a panel of Vpr/Vpx chimeras. Analysis of the chimeras demonstrated that the amino-terminal domain of Vpx is important for the enhancement of infection. Fine mapping of the region indicated that amino acids at positions 9, 12, and 15 to 17 were required. Although the mutants failed to enhance infection, they retained their ability to interact with DCAF1. These findings suggest that the Vpx amino terminus contains an activation domain that serves as the binding site for a cellular restriction factor.

Download Full-text

Mechanism of actin N-terminal acetylation

Science Advances ◽

10.1126/sciadv.aay8793 ◽

2020 ◽

Vol 6 (15) ◽

pp. eaay8793 ◽

Cited By ~ 11

Author(s):

Grzegorz Rebowski ◽

Malgorzata Boczkowska ◽

Adrian Drazic ◽

Rasmus Ree ◽

Marianne Goris ◽

...

Keyword(s):

Ternary Complex ◽

Atomic Resolution ◽

Cellular Proteins ◽

Amino Terminus ◽

Natural Substrate ◽

Filamentous Actin ◽

Actin Isoforms ◽

Substrate Complex ◽

Cellular Analysis ◽

Human Proteins

About 80% of human proteins are amino-terminally acetylated (Nt-acetylated) by one of seven Nt-acetyltransferases (NATs). Actin, the most abundant protein in the cytoplasm, has its own dedicated NAT, NAA80, which acts posttranslationally and affects cytoskeleton assembly and cell motility. Here, we show that NAA80 does not associate with filamentous actin in cells, and its natural substrate is the monomeric actin-profilin complex, consistent with Nt-acetylation preceding polymerization. NAA80 Nt-acetylates actin-profilin much more efficiently than actin alone, suggesting that profilin acts as a chaperone for actin Nt-acetylation. We determined crystal structures of the NAA80-actin-profilin ternary complex, representing different actin isoforms and different states of the catalytic reaction and revealing the first structure of NAT-substrate complex at atomic resolution. The structural, biochemical, and cellular analysis of mutants shows how NAA80 has evolved to specifically recognize actin among all cellular proteins while targeting all six actin isoforms, which differ the most at the amino terminus.

Download Full-text

Heterogeneous Nuclear Ribonucleoprotein A1 and Lamin A/C Modulate Nucleocytoplasmic Shuttling of Avian Reovirus p17

Journal of Virology ◽

10.1128/jvi.00851-19 ◽

2019 ◽

Vol 93 (20) ◽

Cited By ~ 3

Author(s):

Hung-Chuan Chiu ◽

Wei‐Ru Huang ◽

Yu-Yang Wang ◽

Jyun‐Yi Li ◽

Tsai-Ling Liao ◽

...

Keyword(s):

Amino Acids ◽

Nuclear Import ◽

Cellular Proteins ◽

Amino Terminus ◽

Lamin A ◽

Hnrnp A1 ◽

Avian Reovirus ◽

Nucleocytoplasmic Shuttling ◽

Heterogeneous Nuclear Ribonucleoprotein ◽

Nuclear Ribonucleoprotein

ABSTRACT Avian reovirus (ARV) p17 protein continuously shuttles between the nucleus and the cytoplasm via transcription-dependent and chromosome region maintenance 1 (CRM1)-independent mechanisms. Nevertheless, whether cellular proteins modulate nucleocytoplasmic shuttling of p17 remains unknown. This is the first report that heterogeneous nuclear ribonucleoprotein (hnRNP) A1 serves as a carrier protein to modulate nucleocytoplasmic shuttling of p17. Both in vitro and in vivo studies indicated that direct interaction of p17 with hnRNP A1 maps within the amino terminus (amino acids [aa] 19 to 40) of p17 and the Gly-rich region of the C terminus of hnRNP A1. Furthermore, our results reveal that the formation of p17-hnRNP A1-transportin 1 carrier-cargo complex is required to modulate p17 nuclear import. Utilizing sequence and mutagenesis analyses, we have identified nuclear export signal (NES) 19LSLRELAI26 of p17. Mutations of these residues causes a nuclear retention of p17. In this work, we uncovered that the N-terminal 21 amino acids (aa 19 to 40) of p17 that comprise the NES can modulate both p17 and hnRNP A1 interaction and nucleocytoplasmic shuttling of p17. In this work, the interaction site of p17 with lamin A/C was mapped within the amino terminus (aa 41 to 60) of p17 and p17 colocalized with lamin A/C at the nuclear envelope. Knockdown of hnRNP A1 or lamin A/C led to inhibition of nucleocytoplasmic shuttling of p17 and reduced virus yield. Collectively, the results of this study provide mechanistic insights into hnRNP A1 and lamin A/C-modulated nucleocytoplasmic shuttling of the ARV p17 protein. IMPORTANCE Avian reoviruses (ARVs) cause considerable economic losses in the poultry industry. The ARV p17 protein continuously shuttles between the nucleus and the cytoplasm to regulate several cellular signaling pathways and interacts with several cellular proteins to cause translation shutoff, cell cycle arrest, and autophagosome formation, all of which enhance virus replication. To date the mechanisms underlying nucleocytoplasmic shuttling of p17 remain largely unknown. Here we report that hnRNP A1 and lamin A/C serve as carrier and mediator proteins to modulate nucleocytoplasmic shuttling of p17. The formation of p17-hnRNP A1-transportin 1 carrier-cargo complex is required to modulate p17 nuclear import. Furthermore, we have identified an NES-containing nucleocytoplasmic shuttling domain (aa 19 to 40) of p17 that is critical for binding to hnRNP A1 and for nucleocytoplasmic shuttling of p17. This study provides novel insights into how hnRNP A1 and lamin A/C modulate nucleocytoplasmic shuttling of the ARV p17 protein.

Download Full-text

Proto-oncogene FosB: the amino terminus encodes a regulatory function required for transformation.

Molecular and Cellular Biology ◽

10.1128/mcb.13.5.2635 ◽

1993 ◽

Vol 13 (5) ◽

pp. 2635-2643 ◽

Cited By ~ 22

Author(s):

R Wisdom ◽

I M Verma

Keyword(s):

Transcriptional Activation ◽

Leucine Zipper ◽

Regulatory Function ◽

Amino Terminus ◽

Activation Domain ◽

Transcriptional Activation Domain ◽

Constitutive Activation ◽

Functional Conservation ◽

N Terminus ◽

Basic Region

Overexpression of some members of the Fos gene family, including FosB, leads to transformation of established rodent fibroblasts. We have previously shown that transformation by FosB requires the presence of a C-terminal transcriptional activation domain. We now report that transformation by FosB also requires an intact DNA-binding domain composed of the functionally bipartite basic region and leucine zipper as well as sequences present in the N terminus that serve a regulatory function. Deletion of the N-terminal sequences results in proteins impaired in transcriptional activation and transformation. This region does not itself function as a transcriptional activation domain but instead regulates the transactivation functions present in the FosB-Jun complex. The requirement for this N-terminal region can be abolished by the presence of a strong constitutive activation domain. The primary sequence of the region that we have defined is highly conserved in the Fos family of proteins, suggesting functional conservation.

Download Full-text