The nuclear envelope has recently become the object of intense scrutiny because it is the site of nuclear transport and is possibly involved in the organization of the interphase genome, thereby aflecting gene expression. The major structural support for the nuclear envelope is the nuclear lamina, composed of the nuclear lamin proteins. They lie on the surface of the inner nuclear membrane and are in direct contact with the chromatin at the edge of the nucleus. The structure of the nuclear lamin proteins has recently been deduced from their cDNAs and shown to have remarkable homologies to the family of cytoplasmic intermediate $laments. However, the lamin proteins have been found to depolymerize in response to metaphase-specijc phosphorylation events, and reassemble around daughter chromosomes at the completion of cell division. Little is known of the mechanisms of these dynamics, nor of other post-translational modijications evident in these proteins.
In addition, we have as yet no concrete idea of the function of these highly conservedproteins in the cell. This review will summarize our present knowledge of nuclear lamin structure and the new experimental approaches designed to elucidate their function.
REVIEW ARTICLES
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