Nucleoplasmin cDNA sequence reveals polyglutamic acid tracts and a cluster of sequences homologous to putative nuclear localization signals.

Nucleoplasmin is the most abundant protein in the Xenopus oocyte nucleus. It is involved in histone storage and chromatin assembly and it has been used extensively to study the transport of proteins into the cell nucleus. We have isolated lambda gt11 phage containing nucleoplasmin cDNA and have determined the sequence of the entire protein coding region of 200 amino acids for one of the two genes. The translation product of the sp6 transcript of this cDNA has the same electrophoretic mobility as nucleoplasmin and is able to form pentamers. The protein sequence shows remarkable clusters of charged residues including a long polyglutamic acid tract which presumably constitutes the histone binding site. The short C-terminal domain which specifies nuclear entry contains four regions which are homologous to putative nuclear localization signals including two regions of homology to the nuclear migration signal of SV40 large T antigen.