Celeste Ptak

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In Saccharomyces cerevisiae, the evolutionarily conserved nucleocytoplasmic shuttling protein Nap1 is a cofactor for the import of histones H2A and H2B, a chromatin assembly factor and a mitotic factor involved in regulation of bud formation. To understand the mechanism by which Nap1 function is regulated, Nap1-interacting factors were isolated and(More)
Phosphorylation of histone H3 is a hallmark event in mitosis and is associated with chromosome condensation. Here, we use a combination of immobilized metal affinity chromatography and tandem mass spectrometry to characterize post-translational modifications associated with phosphorylation on the N-terminal tails of histone H3 variants purified from(More)
The Ras family of small GTPases regulates cell proliferation, spreading, migration and apoptosis, and malignant transformation by binding to several protein effectors. One such GTPase, R-Ras, plays distinct roles in each of these processes, but to date, identified R-Ras effectors were shared with other Ras family members (e.g., H-Ras). We utilized a new(More)
Phosphatase and tensin homolog (PTEN), deleted on chromosome 10, is a potent tumor suppressor. PTEN expression is reduced in advanced bladder cancer and reduction correlates with disease stage. To gain insights into the function of PTEN in human bladder cancer by identifying its binding partners, we developed a novel IPTG inducible PTEN expression system(More)
We used a TAP-tag approach to identify candidate binding proteins for the related Ras family GTPases: H-Ras, R-Ras, and Rap1A. Protein complexes were isolated from mouse fibroblasts, and component proteins were identified by a combination of nanoflow HPLC and tandem mass spectrometry. H-Ras was found to associate with numerous cytoskeletal proteins(More)
sites mapped by mass spectrometry Boris Ratnikov1,*,‡, Celeste Ptak2,*, Jaewon Han1, Jeffrey Shabanowitz2,3, Donald F. Hunt2,3 and Mark H. Ginsberg1 1Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 920930726 USA 2Department of Chemistry, University of Virginia, Charlottesville, VA 22908, USA 3Department of(More)
An ultralow volume fraction collection system referred to as nano fraction analysis chip technology (nanoFACT) is reported. The system collects 25-2500-nL fractions from 75-microm nanoLC columns into pipet tips at a user-defined, timed interval, typically one fraction every 15-120 s. Following collection, the fractions in the tip dry down naturally on their(More)
Proteomics is undergoing a rapid transformation from a qualitative global peptide sequencing discipline into a quantitative, reproducibility-driven practice. Nowhere is this more evident than in the rapidly expanding field of protein biomarker discovery where the general goal is to uncover statistically robust patterns of differential expression between or(More)
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