The present invention relates to regulation of cellular proliferation. More particularly, the present invention is directed to nucleic acids encoding MRE11, which is a protein involved in modulation of cellular proliferation. The invention further relates to methods for identifying and using agents, including small molecule chemical compositions, antibodies, peptides, cyclic peptides, nucleic acids, antisense nucleic acids, and ribozymes, that modulate cellular proliferation via modulation of MRE11; as well as to the use of expression profiles and compositions in diagnosis and therapy related to modulation of cellular proliferation.