Journal Articles

  • Macrophages eat cancer cells using their own calreticulin as a guide: Roles of TLR and Btk. Proceedings of the National Academy of Sciences of the United States of America Feng, M., Chen, J. Y., Weissman-Tsukamoto, R., Volkmer, J., Ho, P. Y., McKenna, K. M., Cheshier, S., Zhang, M., Guo, N., Gip, P., Mitra, S. S., Weissman, I. L. 2015; 112 (7): 2145-2150


    Macrophage-mediated programmed cell removal (PrCR) is an important mechanism of eliminating diseased and damaged cells before programmed cell death. The induction of PrCR by eat-me signals on tumor cells is countered by don't-eat-me signals such as CD47, which binds macrophage signal-regulatory protein α to inhibit phagocytosis. Blockade of CD47 on tumor cells leads to phagocytosis by macrophages. Here we demonstrate that the activation of Toll-like receptor (TLR) signaling pathways in macrophages synergizes with blocking CD47 on tumor cells to enhance PrCR. Bruton's tyrosine kinase (Btk) mediates TLR signaling in macrophages. Calreticulin, previously shown to be an eat-me signal on cancer cells, is activated in macrophages for secretion and cell-surface exposure by TLR and Btk to target cancer cells for phagocytosis, even if the cancer cells themselves do not express calreticulin.

    View details for DOI 10.1073/pnas.1424907112

    View details for PubMedID 25646432

  • Intraoperative Neuromonitoring in Single-Level Spinal Procedures A Retrospective Propensity Score-Matched Analysis in a National Longitudinal Database SPINE Cole, T., Veeravagu, A., Zhang, M., Li, A., Ratliff, J. K. 2014; 39 (23): 1950-1959
  • Sequence-dependent Structural Variation in DNA Undergoing Intrahelical Inspection by the DNA glycosylase MutM JOURNAL OF BIOLOGICAL CHEMISTRY Sung, R., Zhang, M., Qi, Y., Verdine, G. L. 2012; 287 (22): 18044-18054


    MutM, a bacterial DNA-glycosylase, plays a critical role in maintaining genome integrity by catalyzing glycosidic bond cleavage of 8-oxoguanine (oxoG) lesions to initiate base excision DNA repair. The task faced by MutM of locating rare oxoG residues embedded in an overwhelming excess of undamaged bases is especially challenging given the close structural similarity between oxoG and its normal progenitor, guanine (G). MutM actively interrogates the DNA to detect the presence of an intrahelical, fully base-paired oxoG, whereupon the enzyme promotes extrusion of the target nucleobase from the DNA duplex and insertion into the extrahelical active site. Recent structural studies have begun to provide the first glimpse into the protein-DNA interactions that enable MutM to distinguish an intrahelical oxoG from G; however, these initial studies left open the important question of how MutM can recognize oxoG residues embedded in 16 different neighboring sequence contexts (considering only the 5'- and 3'-neighboring base pairs). In this study we set out to understand the manner and extent to which intrahelical lesion recognition varies as a function of the 5'-neighbor. Here we report a comprehensive, systematic structural analysis of the effect of the 5'-neighboring base pair on recognition of an intrahelical oxoG lesion. These structures reveal that MutM imposes the same extrusion-prone ("extrudogenic") backbone conformation on the oxoG lesion irrespective of its 5'-neighbor while leaving the rest of the DNA relatively free to adjust to the particular demands of individual sequences.

    View details for DOI 10.1074/jbc.M111.313635

    View details for Web of Science ID 000306411600014

    View details for PubMedID 22465958

  • Strandwise translocation of a DNA glycosylase on undamaged DNA PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Qi, Y., Nam, K., Spong, M. C., Banerjee, A., Sung, R., Zhang, M., Karplus, M., Verdine, G. L. 2012; 109 (4): 1086-1091


    Base excision repair of genotoxic nucleobase lesions in the genome is critically dependent upon the ability of DNA glycosylases to locate rare sites of damage embedded in a vast excess of undamaged DNA, using only thermal energy to fuel the search process. Considerable interest surrounds the question of how DNA glycosylases translocate efficiently along DNA while maintaining their vigilance for target damaged sites. Here, we report the observation of strandwise translocation of 8-oxoguanine DNA glycosylase, MutM, along undamaged DNA. In these complexes, the protein is observed to translocate by one nucleotide on one strand while remaining untranslocated on the complementary strand. We further report that alterations of single base-pairs or a single amino acid substitution (R112A) can induce strandwise translocation. Molecular dynamics simulations confirm that MutM can translocate along DNA in a strandwise fashion. These observations reveal a previously unobserved mode of movement for a DNA-binding protein along the surface of DNA.

    View details for DOI 10.1073/pnas.1111237108

    View details for Web of Science ID 000299412600024

    View details for PubMedID 22219368

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