Structural Organization of Dynamic Chromatin

Since 1974, evidence has accumulated in the literature which indicates that chromatin itself may be considered as an assembly system. It is true that chromatin is more complex than assembly systems analyzed to date, both with respect to the size of the nucleic acid involved and therefore the amount (and variety) of protein complexed with it and with respect to the dynamic aspect of the multilevel higher order structure. Nevertheless, at least at the lower levels of organization, the interpretation of chromatin as an assembly system may be valid. Evidence for this derives from three basic lines of research described in previous sections (1) the reconstitution of the nucleosome, (2) the self-assembly of the octamer, and (3) the putative self-organization of nucleosomes into higher order structures. 

Functional analyses have suggested that lamins are involved in a number of biological processes, including DNA replication, chromatin organization, cellular differentiation during development, nuclear envelope reassembly following mitosis, and the structural stabilization of the nuclear membrane during interphase (for review, see Moir et al., 1995). Here we describe two methods that we have successfully applied in our laboratories and that have allowed us to analyze functional and dynamic properties of lamins in vivo by the microinjection of cultured cells with either affinity-purified lamin antibodies or with fluorescently labeled lamins. 

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