Comprehensive Prostate Fluid-Based Spectral Libraries for Enhanced Protein Detection in Urine.

Biofluids contain molecules in circulation and from nearby organs that can be indicative of disease states. Characterizing the proteome of biofluids with DIA-MS is an emerging area of interest for biomarker discovery; yet, there is limited consensus on DIA-MS data analysis approaches for analyzing large numbers of biofluids. To evaluate various DIA-MS workflows, we collected urine from a clinically heterogeneous cohort of prostate cancer patients and acquired data in DDA and DIA scan modes. We then searched the DIA data against urine spectral libraries generated using common library generation approaches or a library-free method. We show that DIA-MS doubles the sample throughput compared to standard DDA-MS with minimal losses to peptide detection. We further demonstrate that using a sample-specific spectral library generated from individual urines maximizes peptide detection compared to a library-free approach, a pan-human library, or libraries generated from pooled, fractionated urines. Adding urine subproteomes, such as the urinary extracellular vesicular proteome, to the urine spectral library further improves the detection of prostate proteins in unfractionated urine. Altogether, we present an optimized DIA-MS workflow and provide several high-quality, comprehensive prostate cancer urine spectral libraries that can streamline future biomarker discovery studies of prostate cancer using DIA-MS.

NF-κB-induced R-loop accumulation and DNA damage select for nucleotide excision repair deficiencies in adult T cell leukemia.

Constitutive NF-κB activation (NF-κBCA) confers survival and proliferation advantages to cancer cells and frequently occurs in T/B cell malignancies including adult T cell leukemia (ATL) caused by human T-cell leukemia virus type 1 (HTLV-1). Counterintuitively, NF-κBCA by the HTLV-1 transactivator/oncoprotein Tax induces a senescence response, and HTLV-1 infections in culture mostly result in senescence or cell-cycle arrest due to NF-κBCA How NF-κBCA induces senescence, and how ATL cells maintain NF-κBCA and avert senescence, remain unclear. Here we report that NF-κBCA by Tax increases R-loop accumulation and DNA double-strand breaks, leading to senescence. R-loop reduction via RNase H1 overexpression, and short hairpin RNA silencing of two transcription-coupled nucleotide excision repair (TC-NER) endonucleases that are critical for R-loop excision-Xeroderma pigmentosum F (XPF) and XPG-attenuate Tax senescence, enabling HTLV-1-infected cells to proliferate. Our data indicate that ATL cells are often deficient in XPF, XPG, or both and are hypersensitive to ultraviolet irradiation. This TC-NER deficiency is found in all ATL types. Finally, ATL cells accumulate R-loops in abundance. Thus, TC-NER deficits are positively selected during HTLV-1 infection because they facilitate the outgrowth of infected cells initially and aid the proliferation of ATL cells with NF-κBCA later. We suggest that TC-NER deficits and excess R-loop accumulation represent specific vulnerabilities that may be targeted for ATL treatment.

RNF8 Dysregulation and Down-regulation During HTLV-1 Infection Promote Genomic Instability in Adult T-Cell Leukemia.

The genomic instability associated with adult T cell leukemia/lymphoma (ATL) is causally linked to Tax, the HTLV-1 viral oncoprotein, but the underlying mechanism is not fully understood. We have previously shown that Tax hijacks and aberrantly activates ring finger protein 8 (RNF8) - a lysine 63 (K63)-specific ubiquitin E3 ligase critical for DNA double-strand break (DSB) repair signaling - to assemble K63-linked polyubiquitin chains (K63-pUbs) in the cytosol. Tax and the cytosolic K63-pUbs, in turn, initiate additional recruitment of linear ubiquitin assembly complex (LUBAC) to produce hybrid K63-M1 pUbs, which trigger a kinase cascade that leads to canonical IKK:NF-κB activation. Here we demonstrate that HTLV-1-infected cells are impaired in DNA damage response (DDR). This impairment correlates with the induction of microscopically visible nuclear speckles by Tax known as the Tax-speckle structures (TSS), which act as pseudo DNA damage signaling scaffolds that sequester DDR factors such as BRCA1, DNA-PK, and MDC1. We show that TSS co-localize with Tax, RNF8 and K63-pUbs, and their formation depends on RNF8. Tax mutants defective or attenuated in inducing K63-pUb assembly are deficient or tempered in TSS induction and DDR impairment. Finally, our results indicate that loss of RNF8 expression reduces HTLV-1 viral gene expression and frequently occurs in ATL cells. Thus, during HTLV-1 infection, Tax activates RNF8 to assemble nuclear K63-pUbs that sequester DDR factors in Tax speckles, disrupting DDR signaling and DSB repair. Down-regulation of RNF8 expression is positively selected during infection and progression to disease, and further exacerbates the genomic instability of ATL.

A Lipidomics Approach to Identifying Key Lipid Species Involved in VEGF-Inhibitor Mediated Attenuation of Bleomycin-Induced Pulmonary Fibrosis.

PURPOSE: Poor molecular characterization of idiopathic pulmonary fibrosis (IPF) has led to insufficient understanding of the pathogenesis of the disease, resulting in lack of effective therapies and poor prognosis. Particularly, the role of lipid imbalance due to impaired lipid metabolism in the pathogenesis of IPF has been poorly studied. EXPERIMENTAL DESIGN: The authors have used shotgun lipidomics in a bleomycin (BLM) mouse model of pulmonary fibrosis with vascular endothelial growth factor (VEGF)-inhibitor CBO-P11 as a therapeutic measure, to identify a comprehensive set of lipids that contribute to the pathogenesis of pulmonary fibrosis. RESULTS: The authors report that attenuation of BLM-induced fibrotic response with CBO-P11 cotreatment is accompanied by a decrease in total lipid content and specific downregulation of lipids, which are upregulated in response to BLM treatment. CONCLUSION AND CLINICAL RELEVANCE: Dysregulated lipids identified in this study hold the potential of being future biomarkers for IPF.

HTLV-1 Infection and Adult T-Cell Leukemia/Lymphoma-A Tale of Two Proteins: Tax and HBZ.

HTLV-1 (Human T-cell lymphotropic virus type 1) is a complex human delta retrovirus that currently infects 10-20 million people worldwide. While HTLV-1 infection is generally asymptomatic, 3%-5% of infected individuals develop a highly malignant and intractable T-cell neoplasm known as adult T-cell leukemia/lymphoma (ATL) decades after infection. How HTLV-1 infection progresses to ATL is not well understood. Two viral regulatory proteins, Tax and HTLV-1 basic zipper protein (HBZ), encoded by the sense and antisense viral transcripts, respectively, are thought to play indispensable roles in the oncogenic process of ATL. This review focuses on the roles of Tax and HBZ in viral replication, persistence, and oncogenesis. Special emphasis is directed towards recent literature on the mechanisms of action of these two proteins and the roles of Tax and HBZ in influencing the outcomes of HTLV-1 infection including senescence induction, viral latency and persistence, genome instability, cell proliferation, and ATL development. Attempts are made to integrate results from cell-based studies of HTLV-1 infection and studies of HTLV-1 proviral integration site preference, clonality, and clonal expansion based on high throughput DNA sequencing. Recent data showing that Tax hijacks key mediators of DNA double-strand break repair signaling-the ubiquitin E3 ligase, ring finger protein 8 (RNF8) and the ubiquitin E2 conjugating enzyme (UBC13)-to activate the canonical nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB) and other signaling pathways will be discussed. A perspective on how the Tax-RNF8 signaling axis might impact genomic instability and how Tax may collaborate with HBZ to drive oncogenesis is provided.

A proteomics approach to identifying key protein targets involved in VEGF inhibitor mediated attenuation of bleomycin-induced pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with a life expectancy of less than 5 years post diagnosis for most patients. Poor molecular characterization of IPF has led to insufficient understanding of the pathogenesis of the disease, resulting in lack of effective therapies. In this study, we have integrated a label-free LC-MS based approach with systems biology to identify signaling pathways and regulatory nodes within protein interaction networks that govern phenotypic changes that may lead to IPF. Ingenuity Pathway Analysis of proteins modulated in response to bleomycin treatment identified PI3K/Akt and Wnt signaling as the most significant profibrotic pathways. Similar analysis of proteins modulated in response to vascular endothelial growth factor (VEGF) inhibitor (CBO-P11) treatment identified natural killer cell signaling and PTEN signaling as the most significant antifibrotic pathways. Mechanistic/mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase (ERK) were identified to be key mediators of pro- and antifibrotic response, where bleomycin (BLM) treatment resulted in increased expression and VEGF inhibitor treatment attenuated expression of mTOR and ERK. Using a BLM mouse model of pulmonary fibrosis and VEGF inhibitor CBO-P11 as a therapeutic measure, we identified a comprehensive set of signaling pathways and proteins that contribute to the pathogenesis of pulmonary fibrosis that can be targeted for therapy against this fatal disease.

HTLV-1 Tax Stimulates Ubiquitin E3 Ligase, Ring Finger Protein 8, to Assemble Lysine 63-Linked Polyubiquitin Chains for TAK1 and IKK Activation.

Human T lymphotropic virus type 1 (HTLV-1) trans-activator/oncoprotein, Tax, impacts a multitude of cellular processes, including I-κB kinase (IKK)/NF-κB signaling, DNA damage repair, and mitosis. These activities of Tax have been implicated in the development of adult T-cell leukemia (ATL) in HTLV-1-infected individuals, but the underlying mechanisms remain obscure. IKK and its upstream kinase, TGFß-activated kinase 1 (TAK1), contain ubiquitin-binding subunits, NEMO and TAB2/3 respectively, which interact with K63-linked polyubiquitin (K63-pUb) chains. Recruitment to K63-pUb allows cross auto-phosphorylation and activation of TAK1 to occur, followed by TAK1-catalyzed IKK phosphorylation and activation. Using cytosolic extracts of HeLa and Jurkat T cells supplemented with purified proteins we have identified ubiquitin E3 ligase, ring finger protein 8 (RNF8), and E2 conjugating enzymes, Ubc13:Uev1A and Ubc13:Uev2, to be the cellular factors utilized by Tax for TAK1 and IKK activation. In vitro, the combination of Tax and RNF8 greatly stimulated TAK1, IKK, IκBα and JNK phosphorylation. In vivo, RNF8 over-expression augmented while RNF8 ablation drastically reduced canonical NF-κB activation by Tax. Activation of the non-canonical NF-κB pathway by Tax, however, is unaffected by the loss of RNF8. Using purified components, we further demonstrated biochemically that Tax greatly stimulated RNF8 and Ubc13:Uev1A/Uev2 to assemble long K63-pUb chains. Finally, co-transfection of Tax with increasing amounts of RNF8 greatly induced K63-pUb assembly in a dose-dependent manner. Thus, Tax targets RNF8 and Ubc13:Uev1A/Uev2 to promote the assembly of K63-pUb chains, which signal the activation of TAK1 and multiple downstream kinases including IKK and JNK. Because of the roles RNF8 and K63-pUb chains play in DNA damage repair and cytokinesis, this mechanism may also explain the genomic instability of HTLV-1-transformed T cells and ATL cells.

BclAF1 restriction factor is neutralized by proteasomal degradation and microRNA repression during human cytomegalovirus infection.

Cell proteins can restrict the replication of viruses. Here, we identify the cellular BclAF1 protein as a human cytomegalovirus restriction factor and describe two independent mechanisms the virus uses to decrease its steady-state levels. Immediately following infection, the viral pp71 and UL35 proteins, which are delivered to cells within virions, direct the proteasomal degradation of BclAF1. Although BclAF1 reaccumulates through the middle stages of infection, it is subsequently down-regulated at late times by miR-UL112-1, a virus-encoded microRNA. In the absence of BclAF1 neutralization, viral gene expression and replication are inhibited. These data identify two temporally and mechanistically distinct functions used by human cytomegalovirus to down-regulate a cellular antiviral protein.

A proteomic study of TAR-RNA binding protein (TRBP)-associated factors.

BACKGROUND: The human TAR RNA-binding protein, TRBP, was first identified and cloned based on its high affinity binding to the small hairpin trans-activation responsive (TAR) RNA of HIV-1. TRBP has more recently been found to be a constituent of the RNA-induced silencing complex (RISC) serving as a Dicer co-factor in the processing of the ~70 nucleotide pre-microRNAs(miRNAs) to 21-25 nucleotide mature miRNAs. FINDINGS: Using co-immunoprecipitation and protein-identification by mass spectrometry, we characterized intracellular proteins that complex with TRBP. These interacting proteins include those that have been described to act in protein synthesis, RNA modifications and processing, DNA transcription, and cell proliferation. CONCLUSIONS: Our findings provide a proteome of factors that may cooperate with TRBP in activities such as miRNA processing and in RNA interference by the RISC complex.

Feature extraction in the analysis of proteomic mass spectra.

Feature extraction or biomarker selection is a critical step in disease diagnosis and knowledge discovery based on protein MS. Many studies have discussed the classification methods applied in proteomics; however, few could be found to address feature extraction in detail. In this paper, we developed a systematic approach for the extraction of mass spectrum peak apex and peak area with special emphasis on noise filtration and peak calibration. Application to a head and neck cancer data generated at the Eastern Virginia Medical School [Wadsworth, J. T., Somers, K. D., Cazares, L. H., Malik, G. et al.., Clin. Cancer Res. 2004, 10, 1625-1632] revealed that the new feature extraction method would yield consistent and highly discriminatory biomarkers.

Impact of HTLV-I Tax on cell cycle progression and the cellular DNA damage repair response.

Human T-cell lymphotropic virus type I (HTLV-I) is the etiologic agent of adult T-cell leukemia (ATL), a rapidly progressing, clonal malignancy of CD4+ T lymphocytes. Fewer than one in 20 infected individuals typically develop ATL and the onset of this cancer occurs after decades of relatively symptom-free infection. Leukemic cells from ATL patients display extensive and varied forms of chromosomal abnormalities and this genomic instability is thought to be a major contributor to the development of ATL. HTLV-I encodes a regulatory protein, Tax, which is necessary and sufficient to transform cells and is therefore considered to be the viral oncoprotein. Tax interacts with numerous cellular proteins to reprogram cellular processes including, but not limited to, transcription, cell cycle regulation, DNA repair, and apoptosis. This review presents an overview of the impact of HTLV-I infection in general, and Tax expression in particular, on cell cycle progression and the repair of DNA damage. The contribution of these activities to genome instability and cellular transformation will be discussed.