Graduate School of Biomedical Sciences, Interdisciplinary Graduate Program
Cell Aging; Human; RNA Processing, Post-Transcriptional; RNA-Binding Proteins; mRNA Cleavage and Polyadenylation Factors; Dissertations, UMMS
Biochemistry, Biophysics, and Structural Biology | Life Sciences | Medicine and Health Sciences
The central dogma of biology asserts that DNA is transcribed into RNA and RNA is translated into protein. However, this overtly simplistic assertion fails to portray the highly orchestrated and regulated mechanisms of transcription and translation. During the process of transcription, RNA provides the template for translation and protein synthesis as well as the structural and sequence specificity of many RNA and protein-based machines. While only 1-5% of the genome will escape the nucleus to be translated as mRNAs, complex, parallel, highly-conserved mechanisms have evolved to regulate specific mRNAs. Trans-acting factors bind cis-elements in both the 5" and 3" untranslated regions of mRNA to regulate their stability, localization, and translation. While a few salient examples have been elucidated over the last few decades, mRNA translation can be reversibly regulated by the shortening and lengthening of the 3" polyadenylate tail of mRNA. CPEB, an important factor that nucleates a complex of proteins to regulate the polyadenylate tail of mRNA, exemplifies a major paradigm of translational control during oocyte maturation and early development. CPEB function is also conserved in neurons and somatic foreskin fibroblasts where it plays an important role in protein synthesis dependent synaptic plasticity and senescence respectively. Focusing on the function of CPEB and its role in mRNA polyadenylation during human cellular senescence, the following dissertation documents the important finding that CPEB is required for the normal polyadenylation of p53 mRNA necessary for its normal translation and onset of senescence. Cells that lack CPEB have abnormal levels of mitochondria and ROS production, which are demonstrated to arise from the direct result of hypomorphic p53 levels. Finally, in an attempt to recapitulate the model of CPEB complex polyadenylation in human somatic cells, I unexpectedly find that Gld-2, a poly(A) polymerase required for CPEB-mediated polyadenylation in Xenopus laevis oocytes, is not required for p53 polyadenylation, but instead regulates the stability of a microRNA that in turn regulates CPEB mRNA translation. Furthermore, I demonstrate that CPEB requires Gld-4 for the normal polyadenylation and translation of p53 mRNA.
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Burns, David M., "Post-Transcriptional Control of Human Cellular Senescence: A Dissertation" (2010). University of Massachusetts Medical School. GSBS Dissertations and Theses. Paper 491.