IL-15 receptor maintains lymphoid homeostasis by supporting lymphocyte homing and proliferation

The IL-15 receptor alpha subunit (IL-15Ralpha) mediates high-affinity binding of IL-15, a pleiotropic cytokine implicated in the development of innate immune cells. We have generated IL-15Ralpha null (IL-15Ralpha-/-) mice to understand the role of IL-15Ralpha in immune development and function. IL-15Ralpha-/- mice are markedly lymphopenic despite grossly normal T and B lymphocyte development. This lymphopenia is due to decreased proliferation and decreased homing of IL-15Ralpha-/- lymphocytes to peripheral lymph nodes. These mice are also deficient in natural killer cells, natural killer T cells, CD8+ T lymphocytes, and TCRgammadelta intraepithelial lymphocytes. In addition, memory phenotype CD8+ T cells are selectively reduced in number. Thus, IL-15Ralpha has pleiotropic roles in immune development and function, including the positive maintenance of lymphocyte homeostasis.

Interleukin-2 receptor alpha chain regulates the size and content of the peripheral lymphoid compartment

Interleukin-2 receptor alpha chain (IL-2R alpha) expression occurs at specific stages of early T and B lymphocyte development and is induced upon activation of mature lymphocytes. Young mice that lack IL-2R alpha have phenotypically normal development of T and B cells. However, as adults, these mice develop massive enlargement of peripheral lymphoid organs associated with polyclonal T and B cell expansion, which, for T cells, is correlated with impaired activation-induced cell death in vivo. Older IL-2R alpha-deficient mice also develop autoimmune disorders, including hemolytic anemia and inflammatory bowel disease. Thus, IL-2R alpha is essential for regulation of both the size and content of the peripheral lymphoid compartment, probably by influencing the balance between clonal expansion and cell death following lymphocyte activation.

An orally bioavailable chemical probe of the Lysine Methyltransferases EZH2 and EZH1

EZH2 or EZH1 is the catalytic subunit of the polycomb repressive complex 2 that catalyzes methylation of histone H3 lysine 27 (H3K27). The trimethylation of H3K27 (H3K27me3) is a transcriptionally repressive post-translational modification. Overexpression of EZH2 and hypertrimethylation of H3K27 have been implicated in a number of cancers. Several selective inhibitors of EZH2 have been reported recently. Herein we disclose UNC1999, the first orally bioavailable inhibitor that has high in vitro potency for wild-type and mutant EZH2 as well as EZH1, a closely related H3K27 methyltransferase that shares 96% sequence identity with EZH2 in their respective catalytic domains. UNC1999 was highly selective for EZH2 and EZH1 over a broad range of epigenetic and non-epigenetic targets, competitive with the cofactor SAM and non-competitive with the peptide substrate. This inhibitor potently reduced H3K27me3 levels in cells and selectively killed diffused large B cell lymphoma cell lines harboring the EZH2(Y641N) mutant. Importantly, UNC1999 was orally bioavailable in mice, making this inhibitor a valuable tool for investigating the role of EZH2 and EZH1 in chronic animal studies. We also designed and synthesized UNC2400, a close analogue of UNC1999 with potency >1,000-fold lower than that of UNC1999 as a negative control for cell-based studies. Finally, we created a biotin-tagged UNC1999 (UNC2399), which enriched EZH2 in pull-down studies, and a UNC1999-dye conjugate (UNC2239) for co-localization studies with EZH2 in live cells. Taken together, these compounds represent a set of useful tools for the biomedical community to investigate the role of EZH2 and EZH1 in health and disease.

Isolation of rat hepatocyte plasma membranes. I. Presence of the three major domains

A rat liver plasma membrane preparation was isolated and characterized both biochemically and morphologically. The isolation procedure was rapid, simple and effective in producing a membrane fraction with the following biochemical characteristics: approximately 40-fold enrichment in three plasma membrane markers, 5'-nucleotidase, alkaline phosphodiesterase I (both putative bile canalicular membrane enzymes), and the asialo-glycoprotein (ASGP) receptor (a membrane glycoprotein present along the sinusoidal front of hepatocytes); a yield of each of these plasma membrane markers that averaged approximately 16%; and minimal contamination by lysosomes, nuclei, and mitochondria, but persistent contamination by elements of the endoplasmic reticulum. Morphological analysis of the preparation revealed that all three major domains of the hepatocyte plasma membrane (sinusoidal, lateral, and bile canalicular) were present in substantial amounts. The identification of sinusoidal membrane was further confirmed when ASGP binding sites were localized predominantly to this membrane in the isolated PM using electron microscope autoradiography. By morphometry, the sinusoidal front membrane accounted for 47% of the total membrane in the preparation, whereas the lateral surface and bile canalicular membrane accounted for 6.8% and 23% respectively. This is the first report of such a large fraction of sinusoidal membrane in a liver plasma membrane preparation.

Bclx regulates the survival of double-positive thymocytes

The bclx gene has been shown to regulate programmed cell death in vitro. We now show that Bclx expression increases dramatically when T cells differentiate from CD4- CD8- (double negative) thymocytes to CD4+ CD8+ [double positive (DP)] thymocytes. In contrast single-positive (SP) thymocytes express negligible amounts of Bclx protein. This expression pattern contrasts with that of Bcl2, which is present in double-negative thymocytes, down-regulated in DP thymocytes, and reinduced upon maturation to SP thymocytes. Elimination of Bclx by gene targeting dramatically shortens the survival of DP thymocytes but not the survival of SP thymocytes or peripheral SP T cells. These data suggest that the induction of Bclx during thymic maturation plays a critical role in regulating the length of time DP thymocytes survive in the absence of selection.

Binding of myc proteins to canonical and noncanonical DNA sequences

Using an in vitro binding-site selection assay, we have demonstrated that c-Myc-Max complexes bind not only to canonical CACGTG or CATGTG motifs that are flanked by variable sequences but also to noncanonical sites that consist of an internal CG or TG dinucleotide in the context of particular variations in the CA--TG consensus. None of the selected sites contain an internal TA dinucleotide, suggesting that Myc proteins necessarily bind asymmetrically in the context of a CAT half-site. The noncanonical sites can all be bound by proteins of the Myc-Max family but not necessarily by the related CACGTG- and CATGTG-binding proteins USF and TFE3. Substitution of an arginine that is conserved in these proteins into MyoD (MyoD-R) changes its binding specificity so that it recognizes CACGTG instead of the MyoD cognate sequence (CAGCTG). However, like USF and TFE3, MyoD-R does not bind to all of the noncanonical c-Myc-Max sites. Although this R substitution changes the internal dinucleotide specificity of MyoD, it does not significantly alter its wild-type binding sequence preferences at positions outside of the CA--TG motif, suggesting that it does not dramatically change other important amino acid-DNA contacts; this observation has important implications for models of basic-helix-loop-helix protein-DNA binding.

A quasi-monoclonal mouse

As a model for studying the generation of antibody diversity, a gene-targeted mouse was produced that is hemizygous for a rearranged V(D)J segment at the immunoglobulin (Ig) heavy chain locus, the other allele being nonfunctional. The mouse also has no functional kappa light chain allele. The heavy chain, when paired with any lambda light chain, is specific for the hapten (4-hydroxy-3-nitrophenyl) acetyl (NP). The primary repertoire of this quasi-monoclonal mouse is monospecific, but somatic hypermutation and secondary rearrangements change the specificity of 20 percent of the antigen receptors on B cells. The serum concentrations of the Ig isotypes are similar to those in nontransgenic littermates, but less than half of the serum IgM binds to NP, and none of the other isotypes do. Thus, neither network interactions nor random activation of a small fraction of the B cell population can account for serum Ig concentrations.

Discovery of a first-in-class EZH2 selective degrader

The enhancer of zeste homolog 2 (EZH2) is the main enzymatic subunit of the PRC2 complex, which catalyzes trimethylation of histone H3 lysine 27 (H3K27me3) to promote transcriptional silencing. EZH2 is overexpressed in multiple types of cancer including triple-negative breast cancer (TNBC), and high expression levels correlate with poor prognosis. Several EZH2 inhibitors, which inhibit the methyltransferase activity of EZH2, have shown promise in treating sarcoma and follicular lymphoma in clinics. However, EZH2 inhibitors are ineffective at blocking proliferation of TNBC cells, even though they effectively reduce the H3K27me3 mark. Using a hydrophobic tagging approach, we generated MS1943, a first-in-class EZH2 selective degrader that effectively reduces EZH2 levels in cells. Importantly, MS1943 has a profound cytotoxic effect in multiple TNBC cells, while sparing normal cells, and is efficacious in vivo, suggesting that pharmacologic degradation of EZH2 can be advantageous for treating the cancers that are dependent on EZH2.

Effect of parathyroid hormone on erythropoiesis

Inhibitors of erythropoiesis have been found in the blood of uremic patients but their nature has not been identified. These patients have excess blood levels of parathyroid hormone (PTH) and it is possible that PTH inhibits erythropoiesis. The present study was undertaken to examine the effect of intact PTH molecules and some of its fragments on human peripheral blood and mouse bone marrow burst-forming units-erythroid (BFU-E), on mouse bone marrow erythroid colony-forming unit (CFU-E), and granulocyte macrophage progenitors (CFU-GM), and evaluate the interaction between PTH and erythropoietin (Ep) on human BFU-E. Intact PTH (1-84 bPTH) in concentrations (7.5-30 U/ml;) comparable to those found in blood of uremic patients produced marked and significant (P less than 0.01) inhibition of BFU-E and mouse marrow GFU-GM, but not of mouse marrow CFU-E. Inactivation of 1-84 bPTH abolished its action on erythropoiesis. Increasing the concentration of Ep in the media from 0.67 to 1.9 U/ml overcame the inhibitory effect of 1-84 bPTH on BFU-E. The N-terminal fragment of PTH (1-34 bPTH) and 53-84 hPTH had no effect on BFU-E. The results demonstrate that (a) either the intact PTH molecule or a C-terminal fragment(s) bigger than 53-84 moiety exerts the inhibitory effect on erythropoiesis, and (b) adequate amounts of Ep can overcome this action of PTH. The data provide one possible pathway for the participation of excess PTH in the genesis of the anemia of uremia.

Dietary L-arginine supplementation normalizes platelet aggregation in hypercholesterolemic humans

OBJECTIVES

The present study was designed to test the hypothesis that long-term dietary supplementation with the nitric oxide precursor L-arginine would enhance vascular or platelet-derived nitric oxide activity, or both, and thereby inhibit platelet reactivity in hypercholesterolemic humans.

BACKGROUND

We have shown that reduced vascular activity of nitric oxide in hypercholesterolemic rabbits can be restored by L-arginine supplementation. The improvement in nitric oxide activity is associated with an inhibition of platelet aggregation ex vivo. This effect is most likely due to increased elaboration of endothelium- or platelet-derived nitric oxide, or both, because the inhibition of platelet reactivity was associated with elevation of intraplatelet cyclic guanosine monophosphate and was reversed by the nitric oxide synthase antagonist N-methyl-arginine.

METHODS

In a double-blinded, randomized, placebo-controlled trial, hypercholesterolemic patients were assigned to L-arginine hydrochloride, 8.4 g/day orally, or placebo for 2 weeks. Platelet-rich plasma was obtained for aggregometry induced by collagen (1 to 10 micrograms/ml) at four points: baseline, after 2 weeks of treatment, after a 2-week washout and after a long-term washout of 16 weeks on average. Aggregation was quantified by light transmittance and expressed as a percent transmittance observed with platelet-poor plasma.

RESULTS

Compared with normocholesterolemic control subjects, platelets from hypercholesterolemic subjects stimulated with 5 micrograms/ml of collagen showed increased aggregability (68.6% in hypercholesterolemic patients vs. 54.5% in normocholesterolemic control subjects, p < or = 0.02). After 2 weeks of treatment with L-arginine (but not placebo), platelet reactivity was modestly reduced; this effect persisted for 2 weeks after discontinuation of arginine (52.6% in arginine-treated patients vs. 65.1% in normocholesterolemic control subjects, p = 0.07). After 18 weeks (i.e., 16 weeks after discontinuing arginine treatment), the platelets of hypercholesterolemic patients once again became hyperaggregable, and the extent of platelet aggregation was significantly increased compared with the 4-week point (73.6% after vs. 52.6% during arginine treatment, p < 0.01). No significant change in platelet reactivity was seen in placebo-treated hypercholesterolemic patients throughout the study. L-Arginine treatment was well tolerated without side effects.

CONCLUSIONS

This double-blinded, placebo-controlled study demonstrates that dietary supplementation with L-arginine can modestly attenuate the increased platelet reactivity seen in hypercholesterolemic patients. The data are consistent with our previous studies in hypercholesterolemic animals, demonstrating that L-arginine restores endogenous nitric oxide activity and inhibits platelet aggregation. Enhancement of endogenous nitric oxide activity is a potential novel therapeutic strategy worthy of further study.

T cells, but not B cells, are required for bowel inflammation in interleukin 2-deficient mice

Interleukin-2 (IL-2)-deficient (IL-2-/-) mice develop anemia and colonic inflammatory bowel disease. To elucidate the mechanism of this disease, we have bred IL-2-/- mice to two strains of immunodeficient mice, RAG-2-deficient (RAG-2-/-, lacking B and T cells) and JH-deficient mice (JH-/-, lacking B cells). IL-2-/-, RAG-2-/- double-mutant mice are disease free, while IL-2-/-, JH-/- double-mutant mice succumb to bowel disease at the same rate as IL-2-/- littermates. IL-2-/-, JH-/- mice do not, however, succumb to anemia. Thus, spontaneous intestinal inflammation in IL-2-/- mice requires mature T cells, not B cells, while anemia is dependent on B cells.

Inhomogeneous backflow transformations in quantum Monte Carlo calculations

An inhomogeneous backflow transformation for many-particle wave functions is presented and applied to electrons in atoms, molecules, and solids. We report variational and diffusion quantum Monte Carlo (VMC and DMC) energies for various systems and study the computational cost of using backflow wave functions. We find that inhomogeneous backflow transformations can provide a substantial increase in the amount of correlation energy retrieved within VMC and DMC calculations. The backflow transformations significantly improve the wave functions and their nodal surfaces.

Conservation of heterochromatin protein 1 function

Heterochromatin represents a cytologically visible state of heritable gene repression. In the yeast, Schizosaccharomyces pombe, the swi6 gene encodes a heterochromatin protein 1 (HP1)-like chromodomain protein that localizes to heterochromatin domains, including the centromeres, telomeres, and the donor mating-type loci, and is involved in silencing at these loci. We identify here the functional domains of swi6p and demonstrate that the chromodomain from a mammalian HP1-like protein, M31, can functionally replace that of swi6p, showing that chromodomain function is conserved from yeasts to humans. Site-directed mutagenesis, based on a modeled three-dimensional structure of the swi6p chromodomain, shows that the hydrophobic amino acids which lie in the core of the structure are critical for biological function. Gel filtration, gel overlay experiments, and mass spectroscopy show that HP1 proteins can self-associate, and we suggest that it is as oligomers that HP1 proteins are incorporated into heterochromatin complexes that silence gene activity.

Regulation of c-SRC activity and function by the adapter protein CAS

SRC family kinases play essential roles in a variety of cellular functions, including proliferation, survival, differentiation, and apoptosis. The activities of these kinases are regulated by intramolecular interactions and by heterologous binding partners that modulate the transition between active and inactive structural conformations. p130(CAS) (CAS) binds directly to both the SH2 and SH3 domains of c-SRC and therefore has the potential to structurally alter and activate this kinase. In this report, we demonstrate that overexpression of full-length CAS in COS-1 cells induces c-SRC-dependent tyrosine phosphorylation of multiple endogenous cellular proteins. A carboxy-terminal fragment of CAS (CAS-CT), which contains the c-SRC binding site, was sufficient to induce c-SRC-dependent protein tyrosine kinase activity, as measured by tyrosine phosphorylation of cortactin, paxillin, and, to a lesser extent, focal adhesion kinase. A single amino acid substitution located in the binding site for the SRC SH3 domain of CAS-CT disrupted CAS-CT's interaction with c-SRC and inhibited its ability to induce tyrosine phosphorylation of cortactin and paxillin. Murine C3H10T1/2 fibroblasts that expressed elevated levels of tyrosine phosphorylated CAS and c-SRC-CAS complexes exhibited an enhanced ability to form colonies in soft agar and to proliferate in the absence of serum or growth factors. CAS-CT fully substituted for CAS in mediating growth in soft agar but was less effective in promoting serum-independent growth. These data suggest that CAS plays an important role in regulating specific signaling pathways governing cell growth and/or survival, in part through its ability to interact with and modulate the activity of c-SRC.

Isolation of rat hepatocyte plasma membranes. II. Identification of membrane-associated cytoskeletal proteins

Rat liver plasma membranes were isolated as presented in the preceding paper (Hubbard, A. L., D. A. Wall, and A. Ma., 1983, J. Cell Biol., 96: 217-229) and found to contain many filaments associated both with desmosomes along the lateral surface and with the cytoplasmic aspects of membranes comprising each of the three domains (lateral [LS], bile canalicular [BC] and sinusoidal [SF] ). Exposure of the plasma membranes to alkaline media (up to pH 11) resulted in loss of recognizable filaments without loss of domain morphology or membrane enzyme activities. Electrophoretic analysis of solubilized components from control and alkaline-extracted plasma membranes revealed that three major polypeptides present at 43, 52, and 56 kdaltons in the control had been released by alkaline treatment (pH 11) and could be quantitatively recovered in the supernate. The 43-kdalton component was identified as cytoplasmic actin by comparison of its tryptic 125I-peptide map to those of muscle (alpha) and brush border (beta, gamma) actins. The 52- and 56-kdalton polypeptides were identified as tonofilament components by their solubility properties and their ability to reassemble into 9.5-nm filaments from monomers present in an alkaline extract.

Short-chain fatty acids induce intestinal epithelial heat shock protein 25 expression in rats and IEC 18 cells

BACKGROUND & AIMS

Because short-chain fatty acids (SCFAs) and heat shock proteins (hsps) confer protection to intestinal epithelia cells (IECs), we studied whether SCFAs modulate IEC hsp expression.

METHODS

Hsp 25, hsp72, and hsc73 protein expression in rat intestinal tissues and IEC-18 cells were determined by Western blot and immunohistochemistry. Cell survival under conditions of oxidant stress (monochloramine) was determined using (51)Cr release in hsp25 cDNA anti-sense and sense-transfected cells expressing minimal and increased hsp25, respectively.

RESULTS

Butyrate induces a time- and concentration-dependent increase in hsp25, but not hsp72 or hsc73, protein expression in rat IEC-18 cells but not 3T3 fibroblasts. Other SCFAs, including the poorly metabolized isobutyate, also induced selective expression of hsp25. Butyrate treatment significantly improved the ability of IEC-18 cells to withstand oxidant (monochloramine) injury. This effect could be blocked in cells in which hsp25 induction by butyrate was blocked by stable hsp25 antisense transfection. Additionally, hsp25-transfected overexpressing IEC-18 cells showed increased resistance to monochloramine. In vivo, increasing dietary fiber increased colonic, but not proximal, ileal hsp25 while having no effect on hsp72 or hsc73 expression.

CONCLUSIONS

SCFAs, the predominant anions of colonic fluid derived from bacterial flora metabolism of luminal carbohydrates, protect IECs against oxidant injury, an effect mediated in part by cell-specific hsp25 induction.

Human papillomavirus infection of the esophagus. A clinicopathologic study with demonstration of papillomavirus antigen by the immunoperoxidase technique

Papillomaviruses are known to be oncogenic in animals. In humans they are associated with benign squamous tumors (verruca, condylomata acuminata, and papillomas) in a variety of body sites. Human papillomavirus (HPV) infection of the esophagus, however, has not previously been documented. Recent reports of condylomatous changes in esophageal epithelium adjacent to esophageal carcinoma and the sporadic descriptions of esophageal papillomas in the literature for many years, lend credence to the assumption that HPV may affect the squamous mucous membrane of the esophagus. In the current study 75 cases, including 2 papillomas and 73 focal epithelial hyperplasia of the esophagus, were examined for histologic evidence of HPV infection as characterized by the presence of koilocytosis, giant and multinucleated cells, dyskeratosis, hyperkeratosis, acanthosis, papillomatosis, and anisonucleosis. Thirteen of the cases--the 2 papillomas and 11 of the focal epithelial hyperplasias--contained distinctive histologic evidence of HPV infection. The presence of HPV antigens was demonstrated by immunoperoxidase (IMPO) in the 4 of the 13 cases (31%). In the remaining cases the IMPO was equivocal in two and negative in seven.

Epigenetic siRNA and Chemical Screens Identify SETD8 Inhibition as a Therapeutic Strategy for p53 Activation in High-Risk Neuroblastoma

Given the paucity of druggable mutations in high-risk neuroblastoma (NB), we undertook chromatin-focused small interfering RNA and chemical screens to uncover epigenetic regulators critical for the differentiation block in high-risk NB. High-content Opera imaging identified 53 genes whose loss of expression led to a decrease in NB cell proliferation and 16 also induced differentiation. From these, the secondary chemical screen identified SETD8, the H4^K20me1 methyltransferase, as a druggable NB target. Functional studies revealed that SETD8 ablation rescued the pro-apoptotic and cell-cycle arrest functions of p53 by decreasing p53^K382me1, leading to activation of the p53 canonical pathway. In pre-clinical xenograft NB models, genetic or pharmacological (UNC0379) SETD8 inhibition conferred a significant survival advantage, providing evidence for SETD8 as a therapeutic target in NB.

Taurocholate stimulates transcytotic vesicular pathways labeled by horseradish peroxidase in the isolated perfused rat liver

The effect of taurocholate on transcytotic vesicular pathways labeled with horseradish peroxidase was assessed in isolated perfused rat liver preparations. Forty-five minutes after a horseradish peroxidase load in a recirculating system, continuous infusion of taurocholate but not taurodehydrocholate significantly increased horseradish peroxidase excretion in bile by 50% compared with controls. When horseradish peroxidase (25 mg) was pulse loaded for 1 minute in control perfusions, it appeared in bile in early (4-6 minutes) and late (20-25 minutes) peaks, the latter accounting for 90% of total horseradish peroxidase output. Taurocholate infusion significantly increased horseradish peroxidase output in both early and late peaks, whereas only a small increase in the early peak was observed with taurodehydrocholate. Colchicine pretreatment increased the early peak in bile but abolished the second peak. Electron micrographs from control livers revealed the accumulation of horseradish peroxidase-containing vesicles in pericanalicular regions at early (2 minutes) as well as late (18 minutes) periods. When a morphometric analysis of electron micrographs was performed from pericanalicular regions 2 minutes after a 1-minute pulse of horseradish peroxidase (500 mg), taurocholate but not taurodehydrocholate increased both the density and percent area of horseradish peroxidase-containing vesicles compared with controls. In contrast, colchicine pretreatment had no effect on the density of the early-appearing vesicles, although their individual sizes were reduced. Taurocholate but not taurodehydrocholate also increased the percent of tubular structures in the pericanalicular region. These findings indicate that taurocholate stimulates both early and late transcytotic vesicle pathways and therefore probably microtubule-independent vesicle pathway is present in hepatocytes that must be distinguished from paracellular routes.

Surface IgM mediated regulation of RAG gene expression in E mu-N-myc B cell lines

Transgenic mice carrying either the c-myc or N-myc oncogene deregulated by the immunoglobulin heavy chain enhancer element (E mu) develop both pre-B and B cell lymphomas (E mu-c-myc and E mu-N-myc lymphomas). We report here that B cell lines derived from these tumors, as well as a line derived from v-myc retroviral transformation, simultaneously express surface immunoglobulin (a hallmark of mature B cells) as well as a common subset of genes normally restricted to the pre-B stage of development-including the recombinase activating genes RAG-1 and RAG-2. Continued RAG-1 and RAG-2 expression in these lines is associated with VDJ recombinase activity detected with a VDJ recombination substrate. Cross-linking of the surface immunoglobulin on these lines with an anti-mu antibody leads to rapid, specific and reversible down-regulation of RAG-1 and RAG-2 gene expression. We also find that a small but significant percentage of normal surface immunoglobulin bearing bone marrow B cells express the RAG-1 gene. These findings are discussed in the context of their possible implications for the control of specific gene expression during the pre-B to B cell transition.

Discovery of a selective, substrate-competitive inhibitor of the lysine methyltransferase SETD8

The lysine methyltransferase SETD8 is the only known methyltransferase that catalyzes monomethylation of histone H4 lysine 20 (H4K20). Monomethylation of H4K20 has been implicated in regulating diverse biological processes including the DNA damage response. In addition to H4K20, SETD8 monomethylates non-histone substrates including proliferating cell nuclear antigen (PCNA) and promotes carcinogenesis by deregulating PCNA expression. However, selective inhibitors of SETD8 are scarce. The only known selective inhibitor of SETD8 to date is nahuoic acid A, a marine natural product, which is competitive with the cofactor. Here, we report the discovery of the first substrate-competitive inhibitor of SETD8, UNC0379 (1). This small-molecule inhibitor is active in multiple biochemical assays. Its affinity to SETD8 was confirmed by ITC (isothermal titration calorimetry) and SPR (surface plasmon resonance) studies. Importantly, compound 1 is selective for SETD8 over 15 other methyltransferases. We also describe structure-activity relationships (SAR) of this series.

Serine phosphorylation of focal adhesion kinase in interphase and mitosis: a possible role in modulating binding to p130(Cas)

Focal adhesion kinase (FAK) is an important regulator of integrin signaling in adherent cells and accordingly its activity is significantly modulated during mitosis when cells detach from the extracellular matrix. During mitosis, FAK becomes heavily phosphorylated on serine residues concomitant with its inactivation and dephosphorylation on tyrosine. Little is known about the regulation of FAK activity by serine phosphorylation. In this report, we characterize two novel sites of serine phosphorylation within the C-terminal domain of FAK. Phosphorylation-specific antibodies directed to these sites and against two previously characterized sites of serine phosphorylation were used to study the regulated phosphorylation of FAK in unsynchronized and mitotic cells. Among the four major phosphorylation sites, designated pS1-pS4, phosphorylation of pS1 (Ser722) is unchanged in unsynchronized and mitotic cells. In contrast, pS3 and pS4 (Ser843 and Ser910) exhibit increased phosphorylation during mitosis. In vitro peptide binding experiments provide evidence that phosphorylation of pS1 (Ser722) may play a role in modulating FAK binding to the SH3 domain of the adapter protein p130(Cas).

Fifth-order raman spectrum of an atomic liquid: simulation and instantaneous-normal-mode calculation

Experimental artifacts and technical difficulties in carrying out theoretical calculations have consistently frustrated attempts to obtain the two-dimensional (5th-order) Raman spectrum of a liquid. We report here a new theoretical development: the first microscopic numerical simulation of the 5th-order Raman signal in a liquid. Comparison with an instantaneous-normal-mode treatment, a fully microscopic model which interprets liquid dynamics as arising from coherent harmonic modes, shows that the 5th-order spectrum reveals profound effects stemming from dynamical anharmonicity.