Date of Award:

5-1-1987

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Biology

Committee Chair(s)

Dennis L. Welker

Committee

Dennis L. Welker

Committee

Bill B. Barnett

Committee

Jeff Kondo

Abstract

Nuclear localization of endogenous plasmids in the cellular slime molds Dictyostelium discoideum and Dictyostelium mucoroides was investigated. Micrococcal nuclease resistant DNA fragments fractionated by gel electrophoresis were present in a banded pattern corresponding to lengths of multiples of approximately 160 bp that have been associated with nucleosome structure in D. discoideum. The same pattern was observed for the plasmids Ddp1 and Ddp2 in D. discoideum as for chromosomal DNA (discoidin genes) and extrachromosomal rDNA (17 S rRNA genes). The presence of the D. discoideum plasmids in chromatin establishes that they are located in the nucleus. Both transcribed and nontranscribed portions of the Ddp1 plasmid were shown to be in nucleosomes in vegetative cells. When D. discoideum was cotransformed with pBMW4 (Ddp1 cloned in pBR322) and BIOS (a pBR322 derivative carrying a G418 resistance gene), the pBR322 sequences were present in nucleosomes indicating that transformed DNA is incorporated into the nucleus. D. mucoroides DNA had a similar banding pattern to that observed with D. discoideum and both D. mucoroides plasmids Dmp1 and Dmp2 were present in nucleosomes. However, with one Dmp2 probe extra bands corresponding to 'half nucleosomes' appeared; this suggests that this region of Dmp2 is not organized into a typical nucleosome structure.

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