Publication Date

1994

Document Type

Dissertation/Thesis

First Advisor

Hubbard, Christopher J.

Degree Name

M.S. (Master of Science)

Department

Department of Biological Sciences

LCSH

Epidermal growth factor||Carcinogenesis

Abstract

Past studies indicate that regulation of epidermal growth factor receptor (EGF-R) mRNA stability plays a major role in EGF-R gene expression. In particular, stimulation of the EGF-R by EGF stabilizes the EGF-R message by a currently undetermined mechanism. The present study was conducted to further evaluate the role that EGF plays in regulating EGF-R stability. KB cells, an epidermal carcinoma cell line, were incubated in serum-free medium for 48 hours in 100 mm culture dishes prior to experimental treatment. Cells were then incubated with various additives after which the transcription inhibitor actinomyin D (Act D) was added and the cells were incubated for an additional period. At the end of each incubation cells were lysed in guanidine lysis buffer or catrimox-14 surfactant and EGF-R mRNA concentrations were measured by RNase protection assay. When cells were stimulated for 5 hours with EGF prior to adding Act D, EGF stabilized the EGF-R message (control half-life = 2.8 hr; +EGF half-life = 4.5 hr). This effect was augmented by cyclohexamide and inhibited by the tyrosine kinase inhibitor lavendustin A. Activating other tyrosine kinase systems showed PDGF to stabilize the message, whereas IGF-I had no effect on EGF-R message decay. The cells were pulsed with EGF (EGF was washed from the medium prior to Act D) for times shorter than 5 hours to determine the length of time required for EGF mediated stabilization of EGF-R message. An exposure time between 1 and 2 hours was required before EGF increased EGF-R mRNA stability beyond that of the controls. These results suggest that EGF stabilizes EGF receptor message through a mechanism involving the EGF receptor tyrosine kinase and protein synthesis. The length of time required for EGF to mediate this event indicates that additional steps beyond tyrosine phosphorylation are required. It is likely that transcription and translation of other proteins which stabilizes the transcript are involved.

Comments

Includes bibliographical references (pages [56]-63)

Extent

63 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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