Exploiting cellular stress as a means to elucidate novel associations at the molecular and cellular systems level
Ippolito, Andrew Joseph
MetadataShow full item record
Protein-protein interactions are one of the principal driving forces behind biomolecular signaling networks. At the cellular level, nonlinear, relationships between sub-compartments are essential for homeostatic maintenance. Therefore, understanding the means through which proteins associate is crucial to gain an accurate and holistic understanding of molecular mechanisms within the cellular complex system. Likewise, elucidating novel relationships between cellular sub-compartments will facilitate a broader understanding as to how the cell persists within harsh extracellular environments. One example includes the relationship between PML nuclear bodies, small punctuate foci interspersed between the interphase chromatin, and the nuclear lamina, an underlying structural and functional component of the nuclear envelope. We have exploited cellular stress as a means to study both molecular and cellular systems. This strategy has been successful in examining the relationship between the IE72 of human Cytomegalovirus and promyelocytic leukemia protein (PML). PML localizes to PML bodies, which are essential for many cellular processes including those involved in stress response, and a target of viral infection. As such, many viral immediate-early proteins localize to these bodies and disrupt them during early infection. While the means by which IE72 disrupts PML bodies is still unknown, recent evidence suggests interaction with PML is crucial. Cytomegalovirus has previously been shown to induce oxidative stress pathways during early infection. Consistent with this, we demonstrate that oxidative stress regulates interaction between PML and IE72, which is blocked by antioxidants. Evidence also suggests that increased association correlates with enhanced cell survival. Extension of these studies to other forms of genotoxic stress revealed a relationship between PML bodies and the lamina. Cells exposed to the doxorubicin have significant perturbations of the nuclear lamina and PML localization. Endogenous PML localized to discrete perinuclear regions devoid of laminar and chromatin staining. Furthermore, overexpression of PML II resulted in a similar, more dramatic phenotype. Evidence is presented that differential sumoylation plays a role in this process. Taken together, our data demonstrate that cellular stress, induced through alteration of the redox state of the cell or by DNA damage, modulates protein-protein interactions, and reveals a functional relationship between two previously unrelated nuclear compartments.