Date of Award
Thesis Professor Department
Biochemistry and Molecular Biology
Jaime Parman-Ryans, Katrina Heil
As the so-called “Mothership of the Human Genome,” the cell nucleus must keep all vital genetic information safe, but accessible, inside a strong protective envelope. The inner membrane of the nuclear envelope is lined by tough but adaptable proteins called lamins. While lamins polymerize into fibrous structures that hold up the “walls” of the nucleus, they also serve as an internal scaffold for the complex machinery involved in DNA replication and gene expression. It is in this later role that we have been looking for clues to premature and possibly to normal aging. One type of lamins, Lamin A is made through an unusual pathway involving a lipid dependent cleavage of a larger precursor called prelamin A. The functional significance of this processing pathway is that prelamin A cannot assemble and is inhibitory of proper lamina formation. Pathological cases of immature lamin A accumulation include Hutchinson-Gilford progeria syndrome (HGPS) or Progeria characterized by premature aging and Restrictive Dermopathy (RD), a lethal prenatal disease. We have previously shown that accumulation of prelamin A leads to cell cycle arrest and drastic changes in expression of genes involved in cell cycle control, among those, several members of the FoxO family of transcription factors.
The goal of this study was to determine the mechanisms by which accumulation of uncleavable prelamin A activates FoxO-mediated cell cycle arrest. Cells expressing an uncleavable form of Lamin A in an inducible manner were used to determine subcellular distribution of FoxO3a upon accumulation of prelamin A. This was done by indirect immunofluorescence and Western blotting. The proliferation rate of these cells and controls expressing wild type Lamin A was also determined by measuring the incorporation of BrdU into DNA.
During these experiments, it was hypothesized and observed that overexpression of prelamin A leads to redistribution of FoxO3a from the cytoplasm of the cell to the nucleoplasm. Expression of FoxO3a target genes was accordingly increased, leading to a decrease in cell proliferation.
The information obtained from this study could not only be of interest in broadening our knowledge of the mechanisms of quiescence and aging in general, but also could inform the discussion of the use of several therapeutics for the treatment of Progeria and other diseases that result from the accumulation of prelamin A.
Honors Thesis - Open Access
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Keasler, Jessica B., "Nuclear Translocation of FoxO3a Transcription Factor During Prelamin A Induced Cell Cycle Arrest in 3T3 Cells." (2012). Undergraduate Honors Theses. Paper 133. http://dc.etsu.edu/honors/133
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