The bi-directional transport of protein and mRNA that occurs through the nuclear pore complex (NPC) in eukaryotic cells is a highly dynamic but highly regulated process. Not only must the cell maintain the proper influx of critical components, such as transcription factors, in response to changing extracellular environments, but it must also maintain the proper efflux of mRNA transcripts for these cellular components to be manufactured in the first place. Interestingly, the precise mechanisms for these processes of protein and mRNA trafficking are still being uncovered. Our overall goal is to understand the mechanisms by which proteins and mRNA transcripts are shuttled between the nucleus and the cytoplasm. Our studies using the genetically tractable yeast, Saccharomyces cerevisiae, have focused on:
HnRNPs and mRNA Export From the Nucleus
In order for a transcript to be exported from the nucleus, it must first undergo several processing steps including the addition of a 5-
Classical Protein Import
Transport of macromolecules in and out of the nucleus occurs through nuclear pore complexes embedded in the nuclear membrane. In addition, a number of soluble factors are required for nucleocytoplasmic transport. A heterodimeric import complex, importin/karyopherin alpha
Ty1 Transposition as Model of HIV
Many retroviruses, like HIV, have developed mechanisms for infecting non-dividing cells such as macrophages. This suggests that the virus has the ability to utilize the cells' nuclear transport machinery to transverse the nuclear membrane and allow access to the chromosomal DNA for viral integration and subsequent replication. However, the mechanism used by HIV to cross the membrane barrier has been widely debated. Because the nuclear membrane does not breakdown during mitosis in yeast we can use the retrotransposon Ty1, an evolutionary relative of retroviruses such as HIV, as a model for retroviral transport and replication. Specifically, we are interested in both the mechanisms of the nuclear import of the Ty1 cDNA/Integrase complex and the nuclear export of Ty1 RNA.