Retroviruses express their repertoire of products from a single primary transcript. However, it appears that the default condition for posttranscriptional processing in a normal cell is to completely splice any intron-containing transcripts. Consequently, the dilemma for the retroviruses is how to export the full length, unspliced and partially spliced transcript which both code for structural proteins, as well as serves as the genome to be packaged into mature virus particles. Many retroviruses (HIV-1, HTLV-l, EIAV, visna) exploit posttranscriptional mechanisms, by which their intron-containing mRNAs circumvent nuclear retention, and are exported to the cytoplasm. For example, HIV-1 RNAs contain at least one functional intron that must enter the cytoplasm to act as templates for the synthesis of proteins. HIV-l regulates expression of its genome through the interaction of a virally encoded trans-acting factor, Rev, with a cis-acting Rev responsive element (RRE). Rev binds unspliced and singly spliced nuclear transcripts containing the RE and shuttles them into the cytoplasm. Other retroviruses (MPMV, SRV) lack Rev-like trans-acting viral proteins. Their transcripts contain a cis-acting element, termed the constitutive transport element (CTE), that allows transport of intron-containing mRNAs. CTE-like elements have also been identified in DNA viruses (Hepatitis B, HSV~1). Retroviral CTEs have been shown to be able to substitute for the Rev/RRE system to allow efficient regulatory control of HIV expression. Although a number of studies have examined what cellular cofactors are involved in Rev/RRE and CTE-mediated transport, it is not clear if common cellular cofactor(s) exist. In these studies we have used a transfection/competition assay to investigate whether Rev/RRE-, SRVCTE~, and MPMVCTE-containing transcripts utilize similar cofactors for nucleocytoplasmic transport. Coexpression of gagMPMVCTE and pCwtRev at various concentrations in the same cell demonstrated that Rev inhibited CTE- mediated transport from the nucleus. Using the same assay we further demonstrated that GTE-mediated export was not inhibited by cotransfection with a pCΔRev(-) mutant clone, a Rev point mutant clone, or luciferase, a non-specific marker protein. Our data suggest that this inhibition is specific for Rev, and for a specific region of the Rev protein. We propose that Rev and the CTEs interact with a common cellular cofactor(s), or that Rev directly interacts with the CTEs.
| Identifer | oai:union.ndltd.org:auctr.edu/oai:digitalcommons.auctr.edu:dissertations-4414 |
| Date | 01 July 2000 |
| Creators | Person, Bridgette D. |
| Publisher | DigitalCommons@Robert W. Woodruff Library, Atlanta University Center |
| Source Sets | Atlanta University Center |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | ETD Collection for AUC Robert W. Woodruff Library |
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