Functional study of the 3' regulatory region of the immunoglobulin heavy chain locus.
Item
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Title
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Functional study of the 3' regulatory region of the immunoglobulin heavy chain locus.
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Identifier
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AAI3314668
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identifier
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3314668
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Creator
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Yan, Yi.
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Contributor
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Adviser: Laurel A. Eckhardt
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Date
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2007
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Molecular
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Abstract
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Chromosome-damaging processes that take place in the immunoglobulin heavy chain (Igh) locus, such as somatic hypermutation (SHM) and DNA rearrangements associated with variable (V) gene assembly and class switch recombination (CSR), are fundamental to the development of a diverse repertoire of B lymphocytes to effectively combat a broad array of harmful pathogens. The cis-acting elements of the Igh locus, including the intronic enhancer Emu and the 3' regulatory region (3'RR) specifically target these events to the Igh locus where benefits outweigh risks. Chromosome translocations representing errors of these precisely-regulated processes are often found in B cell neoplasms. Some of these reciprocal translocations place the MYC gene in cis with the 3'RR. The result is de-regulated MYC expression. We have developed mice transgenic for a human MYC (hMYC) gene under control of the four core enhancers (hs3a, hs1,2, hs3b and hs4) derived from the mouse Igh 3'RR, in order to ask, when, during B cell development, these elements first become active and capable of modifying MYC expression. Unlike other transgenic mouse models where premature and inappropriate MYC expression disrupts normal B cell development, the hMYC transgene in these studies carries a mutation that prohibits MYC protein synthesis. As a result, hMYC expression can be analyzed in all of the normal B cell compartments. Our data show that hMYC is expressed almost exclusively in B-lineage cells and is induced to high levels as soon as bone marrow cells reach the immature B cell stage.;In a separate set of experiments, we have investigated the roles played by two 3'RR enhancers, hs3a and its homolog hs3b, in class switching recombination (CSR). To do this, we generated a BAC (Bacterial Artificial Chromosome) transgene in which hs3a was deleted and hs3b was subject to conditional deletion. The remainder of the BAC construct faithfully mimicked the endogenous Igh locus, carrying a functional Cmu gene and all other C H gene segments, followed by the 3'RR. This BAC was introduced into mice and CSR within the BAC was studied both before and after deletion of hs3b. The preliminary results of this study suggest that these two enhancers are dispensable for both Igmu expression and the process of CSR.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
