Mechanisms and frequencies of HIV recombination.

Mechanisms and frequencies of HIV recombination. We have shown that HIV-1 recombines at very high rates: markers separated by 1.3 kb segregate as unlinked sequences in one round of viral replication. We are currently performing experiments to dissect the mechanisms of recombination and further examine the factors that affect the recombination rates. Another focus of research in our group is the mechanisms of virus assembly and maturation. Multiple elements are required to generate an infectious virus, including the incorporation of virus proteins, viral RNA, and proper maturation of the virion. We are studying virus assembly and maturation using HIV and simple retrovirus model systems: murine leukemia virus (MLV) and spleen necrosis virus (SNV). These projects include: 1) the charged assembly helix motif in MLV, and 2) factors that affect RNA dimer maturation. Charged assembly helix motif in MLV. We have reported a distinct motif, which we termed charged assembly helix motif, at the C terminus of the MLV capsid protein. The amino acids that constitute this motif are rich in both positively and negatively charged amino acids. Our experimental data indicated that this motif forms an alpha helix. Deletion of the entire motif or disturbance of the phases of the helix resulted in virus assembly defects. These defects included the formation of aberrant virus particles that varied widely in size, reduction of the amount of virus generated, and incorporation of the ribosomal RNAs. Taken together, the charged assembly helix plays an important role in virus assembly and regulation of the virus particle size and content. We are currently engaged in further studies to understand the role and function of the charged assembly helix motif in virus assembly. Factors that affect RNA dimer maturation. After virus assembly and budding, the viral RNA dimer undergoes maturation. We are studying the factors involved in this RNA dimer maturation process. Through these studies, we hope to gain a better understanding of HIV replication at various steps. The long-term goals of our research group are to use the understanding of HIV replication to combat the AIDS epidemic.