Precise location of proteins at a given time within a cell is essential
to convey specific signals and result in a relevant functional outcome.
Small ubiquitin-like modifications, such as ubiquitin and SUMO,
represent a delicate and diverse way to transiently regulate
intracellular trafficking events of existing proteins in cells.
Trafficking of multiple proteins is controlled reversibly by ubiquitin
and/or SUMO directly or indirectly via regulation of transport machinery
components. Regulation is dynamic and multilayered, involving active
crosstalk and interdependence between post-translational modifications.
However, in most cases regulation appears very complex, and the
mechanistic details regarding how ubiquitin and SUMO control protein
location in cells are not yet fully understood. Moreover, most of the
findings still lack in vivo evidence in multicellular organisms.