[Current views on function and regulation of Ca2+ levels in cell nuclei].

Ca2+ is involved in the regulation of many events in the nucleus, such as gene expression, DNA replication, DNA repair, chromatin fragmentation in apoptosis, modulation of an intranuclear contractile system. In some cases, the function of Ca2+ is mediated by calmodulin. However, the regulation of nucleoplasmic Ca2+ concentration has not been explored thoroughly. The data discussed in this review show that the [Ca2+]n may be regulated independently of that of cytosolic Ca2+. IP3 and cyclic ADP-ribose are the major factors responsible for Ca2+ release into the nucleus from perinuclear space.