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School of Biology Seminar Series

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Publication Search Results

Now showing 1 - 3 of 3
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    Genetics under geothermal conditions: Homologous recombination in the archaeon Sulfolobus acidocaldarius
    (Georgia Institute of Technology, 2008-10-23) Grogan, Dennis
    Hyperthermophilic archaea differ radically from all model organisms with respect to their evolutionary history and the severe environmental conditions they require. This divergence raises questions as to whether their genetic processes also have unusual properties; but few of these processes have been analyzed in vivo. In the extreme thermoacidophile Sulfolobus acidocaldarius, a conjugational mechanism of DNA transfer enables recombination between chromosomal mutations to be quantified. Early studies of this system suggested a non-reciprocal mechanism in which donor sequences become incorporated into the recipient genome as short segments. Subsequent studies using electroporation found that synthetic oligonucleotides can recombine into this genome. When similar experiments used longer, duplex DNAs containing multiple, silent markers, the resulting recombinants often contained multiple replacement tracts, consistent with an unusual, "short-patch" mode of homologous recombination.
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    Steroidogenesis-inducing protein: An enigmatic protein with multiple biological functions
    (Georgia Institute of Technology, 2008-10-09) Khan, Shafiq A.
    SIP was isolated and characterized from human ovarian follicular fluid in our laboratory on the basis of its profound effects on steroid production in testicular, ovarian and adrenal cells. Later studies showed that SIP is also a potent mitogen and stimulated DNA synthesis in testicular Leydig cells, ovarian granulosa cells and in cell lines derived from ovarian epithelial carcinomas. Partial amino acid sequence analysis of this protein revealed that SIP is a novel protein which shows similarities with immunoglobulins and with a recently characterized DING family of proteins. Antibodies raised against specific SIP peptide blocked the activity of SIP on DNA synthesis and on steroid production in testicular cells. Using these antibodies we also determined the expression of SIP in different tissues and cell lines including prostate cancer cells. A SIP protein was detected in the rat testes, ovarian granulosa cells, ovarian epithelial cancer cell lines and in several prostate cancer cell lines. Furthermore, treatment with purified SIP resulted in induction of proliferation of prostate cancer cells similar to that seen in ovarian cancer cells and in other cell types. Based on these studies we hypothesize that SIP is produced by prostate cancer cells in the advanced stages of disease and serves as an autocrine regulator of cell proliferation in these cells. Furthermore, we hypothesize that SIP may exert its steroidogenic effects on these cells resulting in synthesis of steroids which may serve as ligands for AR and hence may lead to insensitivity to exogenous androgens
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    Visualizing Biological Machines with CryoEM
    (Georgia Institute of Technology, 2008-09-22) Carragher, Bridget
    Over the past decade, cryo-electron microscopy (cryoEM) has emerged as a powerful approach to the structural determination of large macromolecular complexes. Elucidating the structure and mechanism of action of these "molecular machines" is an emerging frontier in understanding how the information in the genome is transformed into cellular activities. In cryoEM the macro molecular specimen is preserved in a thin layer of vitreous (glassy) ice and imaged in the electron microscope using very low doses of electrons. The low signal to noise ratio of the resulting images means that averaging is required to recover the signal and reconstruct a three dimensional map of the structure. Our goal is to develop a pipeline to automate the processes involved in solving macromolecular structures using cryo-electron microscopy. One of the goals of the pipeline is to enable much higher data throughputs and improve the resolution of single particle reconstructions. We are also using the pipeline to help understand what currently limits resolution in these maps. The current status of these efforts will be illustrated using a variety of macromolecules as case studies.