THE CHROMATIN STRUCTURE OF SOME CROWN GALL TUMOR GENES (NUCLEOSOME, TRANSFER-DNA)
Abstract
I have investigated the nucleosome organization and the relative deoxyribonuclease I (DNA'se I) sensitivity of the T-DNA of an octopine-type and a nopaline-type crown gall tumor. The T-DNA of the octopine-type tumor was found to be in an altered nucleosomal array, to be preferentially DNA'se I sensitive over the bulk of the chromatin, and to contain no detectable DNA'se I hypersensitive sites. The T-DNA of the nopaline-type tumor was found in the typical nucleosome array, was preferentially DNA'se I sensitive over the bulk of the chromatin, and was probably lacking any detectable DNA'se I hypersensitive sites. The preferential DNA'se I sensitivity of the T-DNA in both crown gall tumor lines suggests that the majority of the T-DNA in these cell lines is transcriptionally competent. The altered nucleosome array of the octopine-type T-DNA may indicate that the majority of the T-DNA in this line is rapidly transcribed. The plant portion of a plant/T-DNA junction was isolated and characterized. The sequences homologous to the plant portion of the plant/T-DNA junction were found in the typical nucleosome array in the octopine-type tumor. The sequences homologous to the plant portion of the junction fragment did not share the altered nucleosome structure of the majority of the T-DNA in the octopine-type tumor investigated. I have also investigated the nucleosome structure of the rRNA in a variety of Nicotiana cell lines. Of seven tumorous and nontumorous cell lines investigated only the two octopine type crown gall tumors had their rDNA in an altered nucleosomal conformation. A correlation was established between the altered nucleosome structure of the rDNA in a cell line and a substantial reduction of the rDNA copy number in the same cell lines. It is likely that the altered nucleosome structure of the rDNA is a result of rapid transcription of the remaining rDNA necessitated by the reduction in their copy number.
Degree
Ph.D.
Subject Area
Molecular biology
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