Summer Research Description: Dynein is an essential cytoskeletal motor protein, facilitating the transport of various materials within the cell by binding to and trafficking along microtubules. In non-dividing cells, dynein transports cargo from the cell periphery towards the nucleus and microtubule-organizing center, in a microtubule minus-end directed manner. Previous data indicates that dynein plays a role in HIV intracytoplasmic transport. In these studies, I used flow cytometry and X-gal analysis to assess the effects of Ciliobrevin, an inhibitor of dynein ATPase activity, on HIV infectivity. Using flow cytometry, I found that increasing the concentration of Ciliobrevin, gives an overall decrease in infectivity, however not to the extent shown by previous studies, likely due to differences in the approaches used to quantify the extent of infection. This increased inhibition of dynein leads to lowered infectivity because fewer HIV particles are being trafficked to the nucleus. I am also using these techniques to test various HIV capsid mutants for their ability to utilize dynein and infect cells. Structural changes in the capsid mutants compared to wild type could impact HIV-1 utilization of dynein and in turn affect subsequent infectivity rates. By inhibiting dynein through Ciliobrevin, I can determine which capsid mutants have a greater ability to associate with dynein, allowing for greater infectivity. Differences in infectivity between HIV mutant and wild type could be attributed to different viral components that confer better or worse binding capability. Identifying these unique components in the mutants can lead to novel anti-viral targets for HIV trafficking.