Portland State University. Department of Biology
Robert L. Millette
Term of Graduation
Date of Publication
Master of Science (M.S.) in Biology
Nucleotide sequence, Genetic regulation, Herpes simplex virus
1 online resource (ii, 53 pages)
The human c-myc gene is a cellular proto-oncogene composed of three exons and two introns. Transcription of c-myc is controlled by two promoters, P1 and P2. The activity of these promoters is regulated by many factors, such as cellular transcription factors E2F, YY1, and HSV-1 immediate-early proteins, ICP0, ICP4.
Many regulatory elements located both upstream of and between P1 and P2 have been identified, and some of these are required for optimum expression of c-myc. In this thesis research, a region downstream from P2 in the c-myc exon 1 was identified by its response to transactivation by HSV-1 immediate-early proteins, ICP0 and ICP4. The purpose of this research was to examine this region for regulatory sites that respond to HSV-1 infection. I hypothesized that after HSV-1 infection, ICP0 and ICP4 activate c-myc expression, in part, through regulatory sequences present in exon 1.
To test for this hypothesis, reporter plasmids containing (I) the c-myc promoter (from - 101 bp relative to P1) and exon 1 coupled to the bacterial CAT gene were constructed. (ii) The c-myc exon sequences used were either intact (wild-type) or they were constructed with various deletions. The activities of these plasmids were examined in transient expression assays. To analyze protein binding, electrophoretic mobility shift assay (EMSA) and completion EMSAs were carried out. The results from these experiments lead to the following conclusions: (i) ICP4 and ICP0 serve as activators, whereas ICP27 inhibits c-myc gene expression. (ii) The region from +332 to +513 within the c-myc exon 1 contains an important element required for transactivation of the c-myc gene by HSV-1 proteins. (iii) Cellular proteins, including factor YY1, bind to the region from +332 to +513 in the c-myc exon 1.
Although the exact mechanism by which HSV-1 immediate-early proteins regulate c-myc gene expression is still not clear, it gives rise to a possibility that this regulation is caused by turning on or activation of the cellular regulatory proteins by ICP4 and ICP0. The cellular proteins in turn activate the c-myc gene expression by interacting with the ciselement downstream from P2.
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Ye, Shanli, "DNA Sequences Involved in the Regulation of Human c-MYC Gene Expression by Herpes Simplex Virus Type 1 (HSV-1)" (1995). Dissertations and Theses. Paper 5221.