Publications by authors named "O'Shea-Greenfield A"

The leukocyte-specific, cytoskeleton-binding pp52 (LSP-1, WP-34) protein is widely expressed in multiple leukocyte lineages, including B and T lymphocytes, granulocytes, and macrophages. We previously detected a tissue-specific promoter preceding the exon encoding the N terminus of the pp52 leukocyte protein. Here we describe the functional characterization of this promoter and identification of the factors in B and T cells that regulate its activity.

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p55Cdc is a protein identified in cycling mammalian cells. It is highly expressed in proliferating but not in differentiated or growth-arrested cells. Structurally, p55Cdc is similar to the Cdc4 and Cdc20 proteins, which have been proposed to regulate DNA synthesis and mitosis in Saccharomyces cerevisiae.

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Previous studies have identified several biochemical parameters that resolve promoter-specific transcription initiation by RNA polymerase II into distinct steps. We have employed these parameters to compare the mechanisms of initiation mediated through either a TATA box or a transcriptional initiator element. Time course experiments revealed that initiator-mediated transcription in a cell-free extract does not display the lag period typically found with TATA-mediated transcription.

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Transcriptional initiator elements and TATA elements are functionally similar, in that both can act in concert with a Sp1-dependent activator element to direct high levels of accurately initiated transcription. In this study, we have used in vitro transcription experiments to elucidate the relative activities of TATA and initiator. By varying the locations of TATA and initiator elements within a simple promoter, we compared their abilities to localize transcription start sites and to mediate transcriptional activation by Sp1.

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The causative factor(s) of Alzheimer's disease (AD) are presently unknown. However, it has been shown that the number as well as the fraction of high- to low-affinity nicotine binding sites is altered in patients suffering from this disease. This finding, along with the identification of seven genes which code for nicotinic receptors expressed in the mammalian brain, has led to the idea that one nicotinic receptor subtype may be specifically altered in AD.

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We have isolated cDNAs encoding a glutamate receptor subunit, designated GluR5, displaying 40%-41% amino acid identity with the kainate/AMPA receptor subunits GluR1, GluR2, GluR3, and GluR4. This level of sequence similarity is significantly below the approximately 70% intersubunit identity characteristic of kainate/AMPA receptors. The GluR5 protein forms homomeric ion channels in Xenopus oocytes that are weakly responsive to L-glutamate.

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Three closely related genes, GluR1, GluR2, and GluR3, encode receptor subunits for the excitatory neurotransmitter glutamate. The proteins encoded by the individual genes form homomeric ion channels in Xenopus oocytes that are sensitive to glutamatergic agonists such as kainate and quisqualate but not to N-methyl-D-aspartate, indicating that binding sites for kainate and quisqualate exist on single receptor polypeptides. In addition, kainate-evoked conductances are potentiated in oocytes expressing two or more of the cloned receptor subunits.

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We have identified two additional members of the neuronal nicotinic acetylcholine receptor (nAChR)-related gene family. cDNA clones for one new gene, designated alpha 5, were isolated from rat hippocampus and rat PC12 cell line cDNA libraries. The alpha 5 gene encodes a protein of 48,800 daltons (424 amino acids) which exhibits significant overall amino acid sequence identity with the previously cloned rat nAChR subunits alpha 1 (49%), alpha 2 (55%), alpha 3 (52%), and alpha 4 (49%).

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We have isolated a complementary DNA clone by screening a rat brain cDNA library for expression of kainate-gated ion channels in Xenopus oocytes. The cDNA encodes a single protein of relative molecular mass (Mr) 99,800 which on expression in oocytes forms a functional ion channel possessing the electrophysiological and pharmacological properties of the kainate subtype of the glutamate receptor family in the mammalian central nervous system.

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