Silencing of Nuclear Mitotic Apparatus protein (NuMA) accelerates the apoptotic disintegration of the nucleus.
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.
Kivinen
Katri
K
Department of Pathology, University of Turku, Finland. katri.kivinen@utu.fi
Taimen
Pekka
P
Kallajoki
Markku
M
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
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