One of the events leading to a cell's commitment to a new cell cycle resulting in cell division is upregulation of the replication-dependent histone gene family. Our laboratory has previously identified a coding region activating sequence (CRAS) present in all replication-dependent histone genes. Furthermore, we showed that the Yin Yang-1 (YY1) protein binds to the alpha element within the conserved CRAS and that this binding activity is essential for correct regulation of this histone gene family. Thus, YY1 plays a central role in gene regulation in the cell cycle, specifically at the G1/S phase transition. Here, we report a mechanistic link between DNA status in the cell and localization of YY1 in the cell. We present several lines of evidence that support YY1 involvement in cellular life and death processes. Confocal microscopic studies show that YY1 subcellular localization in the cell is responsive to DNA synthesis checkpoint events. At the onset of DNA synthesis as cells enter S phase, YY1 pattern of localization changes from the cytoplasm to the nucleus. Later, past the midpoint of S phase, YY1 is primarily cytoplasmic again. Inhibition of DNA synthesis in CHO cells leads to loss of YY1 in the nucleus, and overriding DNA synthesis checkpoints restores YY1 nuclear localization. Moreover, use of apoptosis-inducing agents in HeLa cells leads to translocation of YY1 to the nucleus, very early in the apoptosis process, and regardless of the status of DNA replication in the cell. These results clearly suggest a role of YY1 in global survival or death processes. Also, in our efforts to understand the events leading to a cell's decision to divide again, we performed genomewide gene expression studies using cells in G1 and S phases of the cell division cycle. Utilizing synchronous cell populations, obtained by mitotic shake-off method, and human microarray gene chips, we identified genes up and down regulated in early time points of the cell cycle. We have previously identified 874 genes to be periodically expressed in the human cell cycle using HeLa cells. Using RNA samples collected every 15 minutes for a period of 2 hours post-mitotically, we present here a detailed gene expression profiling of gene activity after cells exit mitosis and begin entry into a new cycle. We also present evidence from histone array data and analysis of stress-induced and mechanical-stress induced genes to prove that our approach, which utilizes the mitotic shake-off technique, is a stress-free method to synchronize mammalian cells. Replication-dependent histone gene expression is tightly linked to the onset of DNA synthesis in the eukaryotic cell cycle. Understanding the protein-gene regulatory network that precedes and then promotes the expression of this gene family will enable us to better understand the signaling that controls cellular growth and proliferation. / A Dissertation Submitted to the Department of Biological Science in Partial
Fulfillment of the Requirements for the Degree of Doctor of Philosophy. / Spring Semester, 2007. / December 15, 2006. / Histone Genes, Gene Expression, CDNA Microarray, Cell-Cycle, YY1, Apoptosis, Mitotic Shakeoff, Subcellular Localization / Includes bibliographical references. / Myra Hurt, Professor Directing Dissertation; Cathy Levenson, Outside Committee Member; Hank Bass, Committee Member; Lloyd Epstein, Committee Member; Thomas C. S. Keller, III, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_175927 |
| Contributors | Beyrouthy, Maroun J., 1976- (authoraut), Hurt, Myra (professor directing dissertation), Levenson, Cathy (outside committee member), Bass, Hank (committee member), Epstein, Lloyd (committee member), Keller, Thomas C. S. (committee member), Department of Biological Science (degree granting department), Florida State University (degree granting institution) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource, computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
Page generated in 0.0131 seconds