TY - JOUR
T1 - Intranuclear sphingomyelin is associated with transcriptionally active chromatin and plays a role in nuclear integrity
AU - Scassellati, Catia
AU - Albi, Elisabetta
AU - Cmarko, Dusan
AU - Tiberi, Cinzia
AU - Cmarkova, Jana
AU - Bouchet-Marquis, Cedric
AU - Verschure, Pernette J.
AU - Van Driel, Roel
AU - Magni, Mariapia Viola
AU - Fakan, Stanislav
PY - 2010/6
Y1 - 2010/6
N2 - Background information. Sphingomyelin is one of the major phospholipids in the cell nucleus. However, its intranuclear distribution with regard to different functional nuclear domains as well as its possible involvement in the nuclear functional architecture remains to be elucidated. Results. We carried out an ultrastructural cytochemical study of the intranuclear distribution of SM (sphingomyelin) using an in situ binding assay of neutral SMase (sphingomyelinase) conjugated to colloidal gold particles. The enzymatic labelling was carried out on ultrathin sections of different mammalian cells prepared by means of various fixation and resin-embedding protocols. Transmission electron microscopic analysis revealed preferential localization of SM within the PR (perichromatin region), a functionally important nucleoplasmic domain containing sites of pre-mRNA synthesis and processing. In the nucleolus, SM is mostly associated with the dense fibrillar component containing transcriptionally active ribosomal genes. Microinjection of enzymatically active SMase into living cells resulted in a rapid degradation of intranuclear structure. Conclusions. Our observations, supported by biochemical data, provide evidence for the involvement of SM in important nuclear functions. They bring additional information pointing out the PR as an essential functional nuclear domain. Furthermore, they suggest a role for SM in the internal nuclear architecture.
AB - Background information. Sphingomyelin is one of the major phospholipids in the cell nucleus. However, its intranuclear distribution with regard to different functional nuclear domains as well as its possible involvement in the nuclear functional architecture remains to be elucidated. Results. We carried out an ultrastructural cytochemical study of the intranuclear distribution of SM (sphingomyelin) using an in situ binding assay of neutral SMase (sphingomyelinase) conjugated to colloidal gold particles. The enzymatic labelling was carried out on ultrathin sections of different mammalian cells prepared by means of various fixation and resin-embedding protocols. Transmission electron microscopic analysis revealed preferential localization of SM within the PR (perichromatin region), a functionally important nucleoplasmic domain containing sites of pre-mRNA synthesis and processing. In the nucleolus, SM is mostly associated with the dense fibrillar component containing transcriptionally active ribosomal genes. Microinjection of enzymatically active SMase into living cells resulted in a rapid degradation of intranuclear structure. Conclusions. Our observations, supported by biochemical data, provide evidence for the involvement of SM in important nuclear functions. They bring additional information pointing out the PR as an essential functional nuclear domain. Furthermore, they suggest a role for SM in the internal nuclear architecture.
KW - Active chromatin
KW - Intranuclear sphingomyelin
KW - Nuclear integrity
KW - Ultrastructural cytochemistry
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U2 - 10.1042/BC20090139
DO - 10.1042/BC20090139
M3 - Article
C2 - 20095965
AN - SCOPUS:77953445940
VL - 102
SP - 361
EP - 375
JO - Biology of the Cell
JF - Biology of the Cell
SN - 0248-4900
IS - 6
ER -