The combinatorial assembly of protein complexes is at the heart of chromatin biology. Lysine demethylase LSD1(KDM1A)/CoREST beautifully exemplifies this concept. The active site of the enzyme tightly associates to the N-terminal domain of transcription factors of the SNAIL1 family, which therefore can competitively inhibit the binding of the N-terminal tail of the histone substrate. Our enzymatic, crystallographic, spectroscopic, and computational studies reveal that LSD1/CoREST can bind to a hexapeptide derived from the SNAIL sequence through recognition of a positively charged α-helical turn that forms upon binding to the enzyme. Variations in sequence and length of this six amino acid ligand modulate affinities enabling the same binding site to differentially interact with proteins that exert distinct biological functions. The discovered short peptide inhibitors exhibit antiproliferative activities and lay the foundation for the development of peptidomimetic small molecule inhibitors of LSD1.

The development of Histone Deacetylase (HDAC) inhibitors has, until recently, principally been driven by their potential as anti-cancer agents. However, there is emerging evidence that HDAC inhibitors could have utility in the treatment of chronic immune and inflammatory disorders, including rheumatoid arthritis, psoriasis, inflammatory bowel disease, multiple sclerosis, systemic lupus erythematosus, airway hyperresponsiveness and organ transplant rejection. Here we discuss the merits of various, structurally-distinct HDAC inhibitors as potential anti-inflammatory therapeutics and provide examples of the novel medicinal chemistry approaches being undertaken to realize HDAC as a druggable target in this clinical setting.

Epstein-Barr virus (EBV; human herpesvirus 4) poses major clinical problems worldwide. Following primary infection, EBV enters a form of long-lived latency in B lymphocytes, expressing few viral genes, and itpersists for the lifetime of the host with sporadic bursts of viral replication. The switch between latency and replication is governed by the action of a multifunctional viral protein Zta (also called BZLF1, ZEBRA, and Z). Using a global proteomic approach, we identified a host DNA damage repair protein that specifically interacts with Zta: 53BP1. 53BP1 is intimately connected with the ATM signal transduction pathway, which is activated during EBV replication. The interaction of 53BP1 with Zta requires the C-terminal ends of both proteins. A series of Zta mutants that show a wild-type ability to perform basic functions of Zta, such as dimer formation, interaction with DNA, and the transactivation of viral genes, were shown to have lost the ability to induce the viral lytic cycle. Each of these mutants also is compromised in the C-terminal region for interaction with 53BP1. In addition, the knockdown of 53BP1 expression reduced viral replication, suggesting that the association between Zta and 53BP1 is involved in the viral replication cycle.The Epstein-Barr virus (EBV) life cycle is divided temporally into two phases, latency and the lytic cycle. Following the infection of epithelial cells of the oropharynx, EBV enters the lytic cycle, where the expression of approximately 80 genes and numerous rounds of genome replication occur, culminating in the production of infectious virions. The infection of B lymphocytes results in the establishment of viral latency with a restricted gene expression pattern; these cells sporadically enter the lytic cycle and reproduce infectious virus (27,53).The EBV gene BZLF1 has been associated specifically with the disruption of latency (reviewed in references 34 and 50). This gene encodes the protein Zta (ZEBRA, BZLF1, Z), which has an undisputed role in activating the viral lytic cycle. Not only is the enforced expression of Zta in cells harboring the latent virus able to induce the viral lytic cycle, but a mutant virus where BZLF1 has been inactivated also is unable to replicate the viral genome (10). Zta has homology to the bZIP family of transcription factors whose general structure includes a transactivation domain and a bZIP domain consisting of a basic DNA contact region and a coiled-coil dimerization motif, termed a leucine zipper (24,49,50). Zta has a more complex dimerization domain than other bZIP family members, consisting of a dimeric leucine zipper entwined with an adjacent carboxyl-terminal region (35,38,44,50). Zta is multifunctional; through its basic region, it interacts with specific sequence DNA motifs (ZREs) that occur in the promoters of several viral and cellular genes (49) and in the viral origin of lytic replication (Ori-lyt) (46,47). Through its bZIP domain, Zta interacts with cellular transcription factors such as p53, RAR, NF-B, CBP, and C/EBP␣ (7), ...

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Treatment of HER2+ breast cancer with trastuzumab is effective and combination anti-HER2 therapies have demonstrated benefit over monotherapy in the neoadjuvant and metastatic settings. This study investigated the therapeutic potential of targeting the BAG-1 protein co-chaperone in trastuzumab-responsive or -resistant cells. In the METABRIC dataset, BAG-1 mRNA was significantly elevated in HER2+ breast tumors and predicted overall survival in a multivariate analysis (HR = 0.81; p = 0.022). In a breast cell line panel, BAG-1 protein was increased in HER2+ cells and was required for optimal growth as shown by siRNA knockdown. Overexpression of BAG-1S in HER2+ SKBR3 cells blocked growth inhibition by trastuzumab, whereas overexpression of a mutant BAG-1S protein (BAG-1S H3AB), defective in binding HSC70, potentiated the effect of trastuzumab. Injection of a Tet-On SKBR3 clone, induced to overexpress myc-BAG-1S into the mammary fat pads of immunocompromised mice, resulted in 2-fold larger tumors compared to uninduced controls. Induction of myc-BAG-1S expression in two Tet-On SKBR3 clones attenuated growth inhibition by trastuzumab in vitro. Targeting endogenous BAG-1 by siRNA enhanced growth inhibition of SKBR3 and BT474 cells by trastuzumab, while BAG-1 protein-protein interaction inhibitor (Thio-S or Thio-2) plus trastuzumab combination treatment synergistically attenuated growth. In BT474 cells this reduced protein synthesis, caused G1/S cell cycle arrest and targeted the ERK and AKT signaling pathways. In a SKBR3 subpopulation with acquired resistance to trastuzumab BAG-1 targeting remained effective and either Thio-2 or BAG-1 siRNA reduced growth more compared to trastuzumab-responsive parental cells. In summary, targeting BAG-1 function in combination with anti-HER2 therapy might prove beneficial.