Structural basis for recruitment of Rab6-interacting protein 1 to Golgi via a RUN domain.

Small GTPase Rab6 regulates vesicle trafficking at the level of Golgi via recruitment of numerous and unrelated effectors. The crystal structure of Rab6a(GTP) in complex with a 378-residue internal fragment of the effector Rab6IP1 was solved at 3.2 angstroms resolution.

Rab6-interacting protein 1 links Rab6 and Rab11 function.

Rab11 and Rab6 guanosine triphosphatases are associated with membranes of the recycling endosomes (REs) and Golgi complex, respectively. Evidence indicates that they sequentially regulate a retrograde transport pathway between these two compartments, suggesting the existence of proteins that must co-ordinate their functions. Here, we report the characterization of two isoforms of a protein, Rab6-interacting protein 1 (R6IP1), originally identified as a Rab6-binding protein.

The mammalian passenger protein TD-60 is an RCC1 family member with an essential role in prometaphase to metaphase progression.

Passenger proteins migrate from inner centromeres to the spindle midzone during late mitosis, and those described to date are essential both for proper chromosome segregation and for completion of cell cleavage. We have purified and cloned the human passenger protein TD-60, and we here report that it is a member of the RCC1 family and that it binds preferentially the nucleotide-free form of the small G protein Rac1. Using siRNA, we further demonstrate that the absence of TD-60 substantially suppresses overall spindle assembly, blocks cells in prometaphase, and activates the spindle assembly checkpoint.