The biology, structure and thermodynamic properties of (CTG)n and (CGG)n trinucleotide repeats from human hereditary diseases /
Since 1991, 12 human loci, responsible for 10 genetic diseases, have been identified in which a normally polymorphic TR undergoes a mutational event where the length of the repeat expands, in some cases, quite dramatically. To understand the underlying molecular mechanism of this expansion, we cond...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739668961&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Since 1991, 12 human loci, responsible for 10 genetic diseases, have been identified in which a normally polymorphic TR undergoes a mutational event where the length of the repeat expands, in some cases, quite dramatically. To understand the underlying molecular mechanism of this expansion, we conducted a series of experiments presented in this dissertation: i) the effect(s) of MMR in E coli on the stability of CTG, ii) cloning and characterization of plasmids containing short/uninterrupted as well as long/polymorphic CGG, iii) the binding of nucleosomes to CGG, and iv) the structural characteristics of CTG and CGG. We show that a proficient MMR system in E. coli will lead to a decreased stability of long CTG TRS, presumably due to the generation of single-stranded regions and formation of DNA hairpins. The stability was found to be orientation dependent. Furthermore, we report method(s) regarding the cloning and stabilization of long CGGs. The stability was dependent on length, the presence of polymorphisms, the host cell genotype, the orientation of the insert in the vector and the position of the insert relative to the origin of replication. Nucleosome reconstitution experiments using EM suggest that contrary to CTG, the CGG locus acts as an exclusion site for the histone octamer(s), offering a possible explanation for the presence of fragile sites at these loci. Finally, circularization kinetics, helical repeat determination, and PAGE were used to show that the CTG and CGG TRS are intrinsically more flexible than random B-DNA and are preferential domains for the localization of writhe from supercoiling. All these studies, in combination, indicate that duplex (fully base paired) TRS exhibit inherently flexible properties with conformational characteristics which are similar to B-form DNA. |
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| Item Description: | Vita. "Major Subject: Biochemistry". In title, subscripts are used. |
| Physical Description: | xii, 175 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 131-161. |