Ailing Hong’s research while affiliated with The University of Texas Health Science Center at Houston and other places

The architecture of cellular proteins connected to form signaling pathways in response to internal and external cues is much more complex than a group of simple protein-protein interactions. Post translational modifications on proteins (e.g., phosphorylation of serine, threonine and tyrosine residues on proteins) initiate many downstream signaling events leading to protein-protein interactions and subsequent activation of signaling cascades leading to cell proliferation, cell differentiation and cell death. As evidenced by a rapidly expanding mass spectrometry database demonstrating protein phosphorylation at specific motifs, there is currently a large gap in understanding the functional significance of phosphoproteins with respect to their specific protein connections in the signaling cascades. A comprehensive map that interconnects phospho-motifs in pathways will enable identification of nodal protein interactions that are sensitive signatures indicating a disease phenotype from the physiological hemostasis and provide clues into control of disease. Using a novel phosphopeptide microarray technology, we have mapped endogenous tyrosine-phosphoproteome interaction networks in breast cancer cells mediated by signaling adaptor protein GRB2, which transduces cellular responses downstream of several RTKs through the Ras-ERK signaling cascade. We have identified several previously reported motif specific interactions and novel interactions. The peptide microarray data indicate that various phospho-motifs on a single protein are differentially regulated in various cell types and shows global downregulation of phosphoprotein interactions specifically in cells with metastatic potential. The study has revealed novel phosphoprotein mediated signaling networks, which warrants further detailed analysis of the nodes of protein-protein interaction to uncover their biomarker or therapeutic potential.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Post-translational modifications (PTMs) of histones play a critical role in diverse biological processes including chromatin compaction, gene expression and cell differentiation. Among a myriad of PMTs, histone methylation catalyzed by histone methyltransferases (HMTs) has been increasingly recognized as an important player responsible for a major signaling mechanism in eukaryotic cells. This suite of epigenetic modifiers represents a new and promising class of therapeutic targets. In cancer, there is a growing body of evidence that suggests changes in the activity of HMTs (a class of chromatin-modifying enzymes) contribute to the uncontrolled cell proliferation that is a hallmark of this devastating disease. The sequence specificity of the substrates of HMTs under a cellular condition are largely unknown but known targets have been mostly identified through a conventional candidate-based approach by using purified HMTs. However, such an experiment frequently does not reflect what could be occurring in cellular contexts or in vivo. In this study, we designed and synthesized a comprehensive histone peptide microarray (PepArray) on a microfluidic chip which contains 3,919 peptides. The peptides contain nine residues with the methylation sites and mutant sites situated in the middle of the sequence so that each peptide has a unique possibility for modification such as methylation or acetylation. We obtained nuclear extract from the breast cancer cell line T47D, and applied the protein lysates to the histone methylation PepArray chip. After incubation of the chip with a methyl-specific antibody, significant signals were detected at the sites containing peptides corresponding to H2AK74, H3K122, and H4K59. We found null signal at mutant sites where the target lysine(K) was replaced with alanine(A). These results reveal the specific activity profiles of HMTs at defined histone sites in a cellular system. Planned further investigation will compare the different histone methylation or acetylation profiles in the various cellular systems, especially in different cancer systems. The current experiment demonstrates an effective solution to comprehensive studies of epigenetic modification. This information may be translated into therapeutic targets of histone methylation inhibition by focusing on identifying inhibitors of specific HMTs as targets for a new generation of therapeutics. Citation Format: Bing Zhu, Ailing Hong, Chris Hebel, Xiaochuan Zhou, Xiaolian Gao. Site specific profiling of histone methyltransferases in cancer cells using histone peptide microarray containing a comprehensive set of histone peptides. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4235. doi:10.1158/1538-7445.AM2013-4235

GRB2 binding data for all the pY motifs for selected proteins from RTK pathway proteome. (XLS)

Data of selected phosphopeptide probes (PPEPs) from the peptide microarray assay of recombinant SH2 domain protein binding. (XLS)

KEGG pathway analysis of the source peptide probes used in SH2 domain binding assays. (XLS)

Layout file of high affinity phosphopeptides selected from recombinant protein binding assays that are substrates for SH2 domain containing proteins for cell lysate assay. (XLSX)

Layout file of phosphopeptide array of RTK pathway proteins for cell lysate assay. (XLS)

Processed data of GRB2-RTK phosphopeptide microarray consisting of 643 pY sites on for MCF10A, MCF7, T47D and MDA-MB231 cell lines. (XLS)

Molecular classification and annotation of selected phosphomotifs based on respective phosphopeptide data showing strong interaction with endogenous GRB2 from breast normal and cancer cells. (XLS)

We have designed and fabricated a microfluidic reactor array device for massively parallel in-situ synthesis of oligonucleotides (oDNA). The device is made of glass anodically bonded to silicon consisting of three level features: microreactors, microchannels and through inlet/outlet holes. Main challenges in the design of this device include preventing diffusion of photogenerated reagents upon activation and achieving uniform reagent flow through thousands of parallel reactors. The device embodies a simple and effective dynamic isolation mechanism which prevents the intermixing of active reagents between discrete microreactors. Depending on the design parameters, it is possible to achieve uniform flow and synthesis reaction in all of the reactors by proper design of the microreactors and the microchannels. We demonstrated the use of this device on a solution-based, light-directed parallel in-situ oDNA synthesis. We were able to synthesize long oDNA, up to 120 mers at stepwise yield of 98 %. The quality of our microfluidic oDNA microarray including sensitivity, signal noise, specificity, spot variation and accuracy was characterized. Our microfluidic reactor array devices show a great potential for genomics and proteomics researches.