The nucleoskeleton: A permanent structure ct cell nuclei regardless of their transcriptional activity

Nuclear matrix or nucleoskeleton is thought to provide structural basis for intranuclear order. However, the nature of this structure is still uncerta in because of numerous technical difficulties in its visualization. To reve al the "real" morphology of the nucleoskeleton, and to identify possible so urces of structural artifacts, three methods of nucleoskeleton preparations were compared. The nucleoskeleton visualized by all these techniques consi sts of identical elements: nuclear lamina and an inner network comprising c ore filaments and the "diffuse" nucleoskeleton. We then tested if the nucle oskeleton is a stable structure or a transient transcription-dependent stru cture. Incubation with transcription inhibitors (cu-amanitin, actinomycin D , and DRB) for various periods of time had no obvious effect on the morphol ogy of the nucleoskeleton. A typical nucleoskeleton structure was observed also in a physiological model - in transcriptionally inactive mouse 2-cell embryos and in active 8- to 16-cell embryos. Our data suggest that the nucl eoskeleton is a permanent structure of the cell nucleus regardless of the n uclear transcriptional state, and the principal architecture of the nucleos keleton is identical throughout the interphase. (C) 2001 Academic Press.