Targeted Identification of Protein Interactions in Eukaryotic mRNA Translation

To identify protein-protein interactions and phosphorylated amino acid sites in eukaryotic mRNA translation, replicate TAP-MudPIT and control experiments are performed targeting Saccharomyces cerevisiae genes previously implicated in eukaryotic mRNA translation by their genetic and/or functional roles in translation initiation, elongation, termination, or interactions with ribosomal complexes. Replicate tandem affinity purifications of each targeted yeast TAP-tagged mRNA translation protein coupled with multidimensional liquid chromatography and tandem mass spectrometry analysis are used to identify and quantify copurifying proteins. To improve sensitivity and minimize spurious, nonspecific interactions, a novel cross-validation approach is employed to identify the most statistically significant protein-protein interactions. Using experimental and computational strategies discussed herein, the previously described protein composition of the canonical eukaryotic mRNA translation initiation, elongation, and termination complexes is calculated. In addition, statistically significant unpublished protein interactions and phosphorylation sites for S. cerevisiae's mRNA translation proteins and complexes are identified.

p63 establishes epithelial enhancers at critical craniofacial development genes

The transcription factor p63 is a key mediator of epidermal development. Point mutations in p63 in patients lead to developmental defects, including orofacial clefting. To date, knowledge on how pivotal the role of p63 is in human craniofacial development is limited. Using an inducible transdifferentiation model, combined with epigenomic sequencing and multicohort meta-analysis of genome-wide association studies data, we show that p63 establishes enhancers at craniofacial development genes to modulate their transcription. Disease-specific substitution mutation in the DNA binding domain or sterile alpha motif protein interaction domain of p63, respectively, eliminates or reduces establishment of these enhancers. We show that enhancers established by p63 are highly enriched for single-nucleotide polymorphisms associated with nonsyndromic cleft lip ± cleft palate (CL/P). These orthogonal approaches indicate a strong molecular link between p63 enhancer function and CL/P, illuminating molecular mechanisms underlying this developmental defect and revealing vital regulatory elements and new candidate causative genes.

Abstract 2578: Investigating the role of mutant p53 in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a highly aggressive cancer characterized by a high rate of metastasis, limited therapeutic options, and a poor prognosis. However, there is limited information regarding the molecular mechanisms underlying the metastatic properties of ESCC. p53 is one of the most commonly mutated genes in ESCC, and our group has shown that esophageal cells lines expressing a mutation in human p53 shows signs of malignancy and increased invasion in 3D organotypic culture. A mouse model of mutant p53 (R172H) in ESCC is lacking in the field. To elucidate the role of mutant p53 in ESCC we developed a novel mouse model utilizing a genetic and carcinogenic approach. L2cre;p53-/- and p53R172H/- mice were generated and treated with 4NQO in their drinking water for 16 weeks, which resulted in the development of ESCC. Compared to wildtype mice, p53R172H/- mice and p53-/- mice exhibited a decreased tumor latency time, increased tumor frequency and a more severe tumor diagnosis. However, p53R172H/- mice and p53-/- mice displayed similar tumorigenic properties. RNA-seq was performed on cell lines established from wildtype and p53 mouse models and reveled different gene expression profiles between wildtype, p53R172H/-, and p53-/- cells. p53R172H/- cells displayed an increase in mesenchymal and decrease in epithelial marker expression, supporting the idea that they are undergoing EMT. In addition, several endocytic recycling related genes, including Rab11-fip1, Rab25, and Myo5b were downregulated in mutant and null p53 compared to wildtype cells. Further examination of the differing genetic profiles in our mouse models can provide novel insight into the role of mutant p53 in ESCC tumorigenesis and lead to the identification of new therapeutic targets.

Citation Format: Ashley Lento, Apple Long, Veronique Giroux, Qiaosi Tang, Morgan Sammons, Andres Klein-Szanto, Shelly Berger, Anil Rustgi. Investigating the role of mutant p53 in esophageal squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2578. doi:10.1158/1538-7445.AM2017-2578

MLL1 is essential for the senescence-associated secretory phenotype

Capell et al. show that MLL1 inhibition represses expression of critical proproliferative cell cycle regulators required for DNA replication and DNA damage response activation, thus disabling senescence-associated secretory phenotype (SASP) expression. These inhibitory effects of MLL1 on SASP gene expression do not impair oncogene-induced senescence and abolish the ability of the SASP to enhance cancer cell proliferation.

Oncogene-induced senescence (OIS) and therapy-induced senescence (TIS), while tumor-suppressive, also promote procarcinogenic effects by activating the DNA damage response (DDR), which in turn induces inflammation. This inflammatory response prominently includes an array of cytokines known as the senescence-associated secretory phenotype (SASP). Previous observations link the transcription-associated methyltransferase and oncoprotein MLL1 to the DDR, leading us to investigate the role of MLL1 in SASP expression. Our findings reveal direct MLL1 epigenetic control over proproliferative cell cycle genes: MLL1 inhibition represses expression of proproliferative cell cycle regulators required for DNA replication and DDR activation, thus disabling SASP expression. Strikingly, however, these effects of MLL1 inhibition on SASP gene expression do not impair OIS and, furthermore, abolish the ability of the SASP to enhance cancer cell proliferation. More broadly, MLL1 inhibition also reduces “SASP-like” inflammatory gene expression from cancer cells in vitro and in vivo independently of senescence. Taken together, these data demonstrate that MLL1 inhibition may be a powerful and effective strategy for inducing cancerous growth arrest through the direct epigenetic regulation of proliferation-promoting genes and the avoidance of deleterious OIS- or TIS-related tumor secretomes, which can promote both drug resistance and tumor progression.

Negative regulation of the RelA/p65 transactivation function by the product of the DEK proto-oncogene

NF-kappaB-mediated transcriptional activation is controlled at several levels including interaction with coregulatory proteins. To identify new proteins capable of modulating NF-kappaB-mediated activation, a cytoplasmic two-hybrid screen was performed using the p65 C-terminal transactivation domain as bait and identified the product of the DEK proto-oncogene. DEK is a ubiquitous nuclear protein that has been implicated in several types of cancer and autoimmune diseases. DEK appears to function in several nuclear processes including transcriptional repression and modulation of chromatin structure. Our data indicate that DEK functions as a transcriptional corepressor to repress NF-kappaB activity. DEK expression blocked p65-mediated activation of an NF-kappaB-dependent reporter gene and also inhibited TNFalpha-induced activation of the reporter gene. Chromatin Immunoprecipitation (ChIP) assays showed that DEK associates with the promoters of the NF-kappaB-regulated cIAP2 and IL-8 genes in untreated cells and dissociates from these promoters upon NF-kappaB binding in response to TNFalpha treatment. Moreover, the expression levels of an NF-kappaB-dependent reporter gene as well as the NF-kappaB-regulated Mcp-1 and IkappaBalpha genes is increased in DEK-/- cells compared with wild-type cells. ChIP assays on these promoters show enhanced and prolonged binding of p65 and increased recruitment of the P/CAF coactivator. Overall, these data provide further evidence that DEK functions to negatively regulate transcription.

Inhibition of inflammation-induced thermal hypersensitivity by sumatriptan through activation of 5-HT(1B/1D) receptors

Migraine is effectively treated by drugs acting via 5-HT(1B/1D) receptors; however, the antinociceptive effects of such agents have not been fully investigated, particularly in models in which sensitization may be present. The aim of these studies was to evaluate the effects of the 5-HT(1B/1D) receptor agonist sumatriptan in specific models of pain states: a mouse model of inflammation-induced thermal hyperalgesia and a rat model of nerve injury-induced thermal hyperalgesia. In female mice, following intraplantar injection of carrageenan 225 min earlier, sumatriptan (300 microg/kg intraperitoneally; i.p.) increased paw withdrawal latency (PWL) from 3.1 +/- 0.4 s in the saline group to 5.6 +/- 0.9 s, measured 240 min postcarrageenan (P < 0.05 ANOVA followed by post hoc Dunnett's test). A similar effect was seen in male mice. Sumatriptan was also effective in male mice when given i.p. and subcutaneously 15 min precarrageenan, with a maximum effect at 30 microg/kg (i.p. latency 7.4 +/- 1.3 s compared to saline group, 2.6 +/- 0.7 s; i.v. latency 5.9 +/- 0.8 s compared to saline group, 2.9 +/- 0.3 s; P < 0.05 ANOVA followed by post hoc Dunnett's test). The number of mice required to give a response that could be reliably attributed to sumatriptan (number needed to treat) was calculated using discriminant analysis and found to be 2.6. The ability of sumatriptan to attenuate the carrageenan-induced reduction in PWL was blocked by the mixed 5-HT(1B/1D) receptor antagonist GR-127935 (3 mg/kg i.p.) but not by the 5-HT(1B) receptor antagonist SB-224289 (10 mg/kg i.p.). Sumatriptan had no effect on thermal hyperalgesia induced by sciatic nerve ligation in the rat at any time point. These data demonstrate that sumatriptan attenuates the hypersensitivity to noxious thermal stimuli induced by intraplantar carrageenan.

Efficacy of a brief psychosocial treatment for panic disorder in an active duty sample: implications for military readiness

OBJECTIVE

The efficacy of a brief cognitive-behavioral treatment for panic in military personnel was evaluated.

METHOD

Active duty military patients (N = 37) presenting at outpatient psychiatry and psychology clinics were randomly assigned to immediate or delayed treatment conditions. All patients met Diagnostic and Statistical Manual of Mental Disorders criteria for a primary diagnosis of panic disorder with or without agoraphobia.

RESULTS

At posttreatment, 80% of the immediate treatment group, compared to 0% of the delayed treatment group, met recovery criteria on all major clinical facets of panic disorder (i.e., panic attacks, panic-related worry, phobic avoidance). At follow-up, 75% of the treated group continued to meet recovery criteria, suggesting maintenance of treatment gains. A majority of those patients (58%) taking benzodiazepines at the start of treatment were successfully discontinued by posttreatment.

CONCLUSIONS

Brief, skill-based treatments for panic disorder are effective for a majority of active duty personnel. These treatments may also improve military readiness by facilitating benzodiazepine discontinuation.