A search for a protein(s) interacting with the block of proliferation 1 (Bop1) protein of Giardia lamblia led to the isolation of end binding (EB1) protein 1, a protein that is known to function as a microtubule (MT) plus-end-tracking protein in other organisms. Interaction between Bop1 and EB1 of G. lamblia was confirmed by co-immunoprecipitation of in vitro-synthesized Bop1 and EB1 proteins. This result suggests coordination between ribosome biogenesis and cell cycle-related processes such as mitosis.