<P> The nuclear envelope acts as a barrier that prevents both DNA and RNA viruses from entering the nucleus . Some viruses require access to proteins inside the nucleus in order to replicate and / or assemble . DNA viruses, such as herpesvirus replicate and assemble in the cell nucleus, and exit by budding through the inner nuclear membrane . This process is accompanied by disassembly of the lamina on the nuclear face of the inner membrane . </P> <P> Initially, it has been suspected that immunoglobulins in general and autoantibodies in particular do not enter the nucleus . Now there is a body of evidence that under pathological conditions (e.g. lupus erythematosus) IgG can enter the nucleus . </P> <P> Most eukaryotic cell types usually have a single nucleus, but some have no nuclei, while others have several . This can result from normal development, as in the maturation of mammalian red blood cells, or from faulty cell division . </P> <P> An anucleated cell contains no nucleus and is, therefore, incapable of dividing to produce daughter cells . The best - known anucleated cell is the mammalian red blood cell, or erythrocyte, which also lacks other organelles such as mitochondria, and serves primarily as a transport vessel to ferry oxygen from the lungs to the body's tissues . Erythrocytes mature through erythropoiesis in the bone marrow, where they lose their nuclei, organelles, and ribosomes . The nucleus is expelled during the process of differentiation from an erythroblast to a reticulocyte, which is the immediate precursor of the mature erythrocyte . The presence of mutagens may induce the release of some immature "micronucleated" erythrocytes into the bloodstream . Anucleated cells can also arise from flawed cell division in which one daughter lacks a nucleus and the other has two nuclei . </P>

Where is the nucleus found in the cell