Date of Award

11-1-1995

Document Type

Thesis

Degree Name

Master of Arts (MA)

Department

Biology

First Advisor

Dr. William Tapprich

Abstract

5-Fluorouracil (FUra), a chemotherapeutic agent, affects the growth of several kinds of tumor cells. It is known to affect DNA as well as RNA. Using Escherichia coli, this study has shown that FUra interferes with the synthesis and assembly of ribosomes. Cells treated in FUra concentrations between 25 ug/ml and 50 ug/ml gave severely retarded growth rates. Sucrose density gradient absorbance profiles of ribosomes from FUra-treated cells indicated altered structural and functional properties. These profiles showed large pools of free ribosomal subunits and few completely associated ribosomes or polyribosomes. The 23S rRNA from FUra-treated ribosomes showed an increases amount of degradation, consistent with previous studies. However, the 16S rRNA and the 30S ribosomal fraction showed no evidence of breakdown products. Composite gel electrophoresis of FUra-treated samples indicated a decrease in S1 protein, a factor which is vital for translation. Analysis of ribosomal proteins revealed that most proteins were present in normal stoichiometries. However, some non-ribosomal proteins associated with unfolded ribosomal particles were present in samples with higher concentrations of FUra. Incorporation studies, showed that 3H-FUra was efficiently incorporated into cells and ribosomes. Incorporation into 30S and 50S subunits was equivalent, but with increased exposure, increasing amounts were incorporated into the translating pool of ribosomes (70S and polyribosomes). The absorbance profiles also showed more assembled ribosomes and polyribosomes with increasing exposure, suggesting that a transient effect on some cellular factor, may have been overcome.

Comments

A Thesis Presented to the Department of Biology and the Faculty of the Graduate College University of Nebraska In Partial Fulfillment of the Requirements for the Degree M.A. in Biology University of Nebraska at Omaha. Copyright 1995 Susan P. Belleh.

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