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Dennis T. Brown
William Neal Reynolds Professor

BA Chemistry/Biology, University of Pennsylvania, 1964
Ph.D. Molecular Biology, University of Pennsylvania, 1967

Email: dennis_brown@ncsu.edu
Office: 346  Polk Hall
Phone: 919-515-5765 (office)
Fax: 919-515-2047

My laboratory investigates the structure, function and assembly of the model membrane containing virus Sindbis. Sindbis virus is the prototype of the alpha viruses, a group of infectious agents which are transmitted in nature by blood sucking insects. The alphaviruses are simple in composition (composed of multiple copies of three proteins) but complex in structure. The virus is made up of two structurally identical icosahedral protein shells between which is sandwiched a membrane bilayer.   The two protein shells are connected to one another by protein-protein interactions which span the membrane bilayer. The protein associations result in a very strong but metastable structure capable of rapidly disassembling to release its genetic material (a single strand of RNA) into a host cell upon contacting an appropriate receptor.

The structure of the mature virion is being determined at high resolution using Electron Cryo-Microscopy. This technology uses massively parallel computers to analyze images of viruses obtained in high voltage electron microscopes equipped with liquid nitrogen stages and field emission guns. Data obtained by morphological studies are verified by biophysical and biochemical analysis of protein configuration and protein/protein associations in the virus structure. Our goal is to produce an image of the structure of this membrane containing virus at atomic resolution.

We are determining the pathway by which virus components are folded and associate with one another inside of the infected cell as the infectious virion is assembled from its component parts. We have determined that the two membrane glycoproteins which make up the outer icosahedral shell pass through a number of complex disulfide bridged intermediates as they are combined into the functional virion. The techniques of molecular and cellular biology together with molecular cloning and site directed mutagenesis are employed to elucidate the pathway of virus assembly. [description of Sindbis virus assembly]

Because the alphaviruses are vectored by insects they must be able to replicate in cells of both vertebrate and invertebrate origin. This has provided us with the opportunity to examine the expression of a single piece of genetic material (the virus RNA) in two phylogeneticaly unrelated biochemical and genetic environments. The expression of the virus genome has dramatically different consequences in the two host cell types in both the manner in which the cells respond to infection (vertebrate cells are killed, insect cells are not killed), and in the manner in which the virus is assembled within the two hosts. We are presently examining alterations in the pattern of cellular gene expression as the insect cell responds to virus infection by establishing a persistently infected state.