The interrelationship of adenovirus infection and host cell microtubule dynamics

A productive adenovirus infection requires that internalized virus particles translocate along microtubules to the nucleus, where replication of the viral genome occurs. Adenovirus-mediated activation of RhoGTPases has been identified as having a role in actin cytoskeletal rearrangements which facilitate adenovirus endocytosis. Before the inception of this research, a complete characterization of the effects of adenovirus infection on the host cell microtubule network had not been undertaken.;Here I have shown that adenovirus infection induces specific changes to both stable and dynamic populations of host cell microtubules. Adenovirus-infected cells had elevated levels of acetylated and detyrosinated microtubules compared to uninfected cells. The accumulation of posttranslationally modified microtubules within adenovirus-infected cells required active RhoA. Contrary to common speculation, I have shown that the efficiency of adenovirus nuclear directed motility is independent of RhoA signaling or microtubule acetylation state. Furthermore, I have shown that adenovirus nuclear directed motility is insensitive to either suppression or enhancement of microtubule dynamicity. Instead, conditions which alter the organization of the microtubule array or prevent microtubule extension to the periphery tend to decrease adenovirus nuclear localization efficiency.;Upon characterizing the dynamic behavior of microtubules within live cells, I found that adenovirus-infection resulted in a transient enhancement of centrosomal microtubule nucleation frequency. At the periphery of adenovirus-infected cells, the dynamic instability of microtubule plus ends shifted toward net growth compared to the nearly balanced growth and shortening observed in uninfected cells. In adenovirus-infected cells, microtubules spent more time in growth, less time in shortening, and underwent catastrophes less frequently compared to those in uninfected cells. The virus-induced shifts in microtubule dynamic instability at the cell periphery required the activity of Rac1. Unlike RhoA, Rac1 activity was required for efficient nuclear-directed motility of adenovirus, suggesting that the adenovirus-induced, Rac1-mediated formation of persistently growing "pioneer-like" microtubules enhances the ability of microtubules to "search and capture" incoming viruses. This is the first characterization of virus-induced changes to host cell microtubule dynamic instability and provides new insight into how various aspects of microtubule dynamic behavior influences virus intracellular motility.