title: Silencing of Nuclear Mitotic Apparatus protein (NuMA) accelerates the apoptotic disintegration of the nucleus.
abstract: One main feature of apoptosis is the sequential degradation of the nuclear structure, including the fragmentation of chromatin and caspase-mediated cleavage of various nuclear proteins. Among these proteins is the Nuclear Mitotic Apparatus protein (NuMA) which plays a specific role in the organization of the mitotic spindle. The exact function of NuMA in the interphase nucleus is unknown, but a number of reports have suggested that it may play a role in chromatin organization and/or gene expression. Here we show that upon cleavage in apoptotic cells, the N-terminal cleavage fragment of NuMA is solubilized while the C-terminal fragment remains associated with the condensed chromatin. Using pancaspase inhibitor z-VAD-fmk and caspase-3 deficient MCF-7 cells, we further show that the solubilization is dependent on caspase-mediated cleavage of NuMA. Finally, the silencing of NuMA by RNAi accelerated nuclear breakdown in apoptotic MCF-7 cells. These results suggest that NuMA may provide structural support in the interphase nucleus by contributing to the organization of chromatin.
authors.affiliation: Department of Pathology, University of Turku, Finland. katri.kivinen@utu.fi
authors.forename: Katri
authors.initials: K
authors.lastname: Kivinen
authors.forename: Pekka
authors.initials: P
authors.lastname: Taimen
authors.forename: Markku
authors.initials: M
authors.lastname: Kallajoki
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000378:metabolism; D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D061945:Caspase Inhibitors; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000378:metabolism; D020868:Gene Silencing; D006801:Humans; D034521:Nuclear Matrix-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D034961:Antigens, Nuclear; D061945:Caspase Inhibitors; D018797:Cell Cycle Proteins; D002843:Chromatin; D015853:Cysteine Proteinase Inhibitors; C050045:NUMA1 protein, human; D034521:Nuclear Matrix-Associated Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D053148:Caspase 3