TRIM5α Cytoplasmic Bodies Are Highly Dynamic Structures

Abstract

Tripartite motif (TRIM)5α has recently been identified as a host restriction factor that has the ability to block infection by certain retroviruses in a species-dependent manner. One interesting feature of this protein is that it is localized in distinct cytoplasmic clusters designated as cytoplasmic bodies. The potential role of these cytoplasmic bodies in TRIM5α function remains to be defined. By using fluorescent fusion proteins and live cell microscopy, we studied the localization and dynamics of TRIM5α cytoplasmic bodies. This analysis reveals that cytoplasmic bodies are highly mobile, exhibiting both short saltatory movements and unidirectional long-distance movements along the microtubule network. The morphology of the cytoplasmic bodies is also dynamic. Finally, photobleaching and photoactivation analysis reveals that the TRIM5α protein present in the cytoplasmic bodies is very dynamic, rapidly exchanging between cytoplasmic bodies and a more diffuse cytoplasmic population. Therefore, TRIM5α cytoplasmic bodies are dynamic structures more consistent with a role in function or regulation rather than protein aggregates or inclusion bodies that represent dead-end static structures.