title: Involvement of the telomeric protein Pin2/TRF1 in the regulation of the mitotic spindle.
abstract: Pin2/TRF1 was independently identified as a telomeric DNA-binding protein (TRF1) that regulates telomere length, and as a protein (Pin2) that can bind the mitotic kinase NIMA and suppress its lethal phenotype. We have previously demonstrated that Pin2/TRF1 levels are cell cycle-regulated and its overexpression induces mitotic arrest and then apoptosis. This Pin2/TRF1 activity can be potentiated by microtubule-disrupting agents, but suppressed by phosphorylation of Pin2/TRF1 by ATM; this negative regulation is critical in mediating for many, but not all, ATM-dependent phenotypes. Interestingly, Pin2/TRF1 specifically localizes to mitotic spindles in mitotic cells and affects the microtubule polymerization in vitro. These results suggest a role of Pin2/TRF1 in mitosis. However, nothing is known about whether Pin2/TRF1 affects the spindle function in mitotic progression. Here we characterized a new Pin2/TRF1-interacting protein, EB1, that was originally identified in our yeast two-hybrid screen. Pin2/TRF1 bound EB1 both in vitro and in vivo and they also co-localize at the mitotic spindle in cells. Furthermore, EB1 inhibits the ability of Pin2/TRF1 to promote microtubule polymerization in vitro. Given that EB1 is a microtubule plus end-binding protein, these results further confirm a specific interaction between Pin2/TRF1 and the mitotic spindle. More importantly, we have shown that inhibition of Pin2/TRF1 in ataxia-telangiectasia cells is able to fully restore their mitotic spindle defect in response to microtubule disruption, demonstrating for the first time a functional involvement of Pin2/TRF1 in mitotic spindle regulation.
authors.affiliation: Cancer Biology Program, Division of Hematology/Oncology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, HIM 1047, Boston, MA 02215, USA. klu@caregroup.harvard.edu
authors.forename: Masafumi
authors.initials: M
authors.lastname: Nakamura
authors.forename: X Z
authors.initials: XZ
authors.lastname: Zhou
authors.forename: Shuji
authors.initials: S
authors.lastname: Kishi
authors.forename: K P
authors.initials: KP
authors.lastname: Lu
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D001260:Ataxia Telangiectasia / Q000378:metabolism; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D005982:Glutathione Transferase / Q000235:genetics; D006367:HeLa Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D008870:Microtubules / Q000737:chemistry / Q000378:metabolism; D008938:Mitosis / Q000187:drug effects; D011485:Protein Binding / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000187:drug effects / Q000378:metabolism*; D016615:Telomere / Q000378:metabolism*; D035321:Telomeric Repeat Binding Protein 1; D014162:Transfection; D025521:Tumor Suppressor Proteins
chemical_list: D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C405804:EB1 microtubule binding proteins; D008164:Luminescent Proteins; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; D035321:Telomeric Repeat Binding Protein 1; D025521:Tumor Suppressor Proteins; D005982:Glutathione Transferase; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases