Nathan A. Hagan University of Maryland, Baltimore County Office: 410-455-3867 FAX: 410-455-2608 E-mail: nhagan1@umbc.edu Job Title: Graduate Student Ph.D. in Chemistry (Expected December, 2005) from the University of Maryland, Baltimore County

Speaker: Nathan A. Hagan, Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore, MD

Topic: Characterization of Protein-RNA Complexes in the HIV-1 Packaging Signal

Place: Building 549, Auditorium, NCI at Frederick, Frederick, MD

Time: Tuesday, March 8, 2005, at 2:00 PM

Abstract: The nucleocapsid (NC) domain of the gag protein plays a critical role in HIV-1 genome dimerization and packaging through noncovalent interactions with a highly conserved, ~120 nt region of retroviral genomic RNA, called the packaging signal (psi-RNA). Due to the low frequency of mutation within this region of the genome and to the critical role that that these RNA-RNA and protein-RNA interactions play in the life cycle of the virus, this has the potential to be a prime target for antiretroviral therapeutics. However, these binding events are not well understood and present an important and challenging system to study by electrospray ionization mass spectrometry (ESI-MS). Using ESI-MS, which is known to preserve the fragile noncovalent protein-RNA interactions, we have performed binding studies of NC with each of the individual hairpin structures that make up the psi-RNA to determine binding stoichiometries and affinities. Mutated RNA constructs have also been utilized in competitive binding experiments to obtain information concerning the facets affecting binding. Taking advantage of the high mass limits and resolving power of ESI-MS, these techniques are currently being applied to study the complex between NC and the complete psi-RNA. A clearer understanding of the determinants of binding between psi-RNA (both individual stem loops and full psi-RNA) and NC would provide valuable information concerning the mechanism and sequence of events taking place during genome dimerization and packaging and could lead to the development of antiretroviral agents that are capable of interfering with this key step.