Disease relevance of npm-A

• 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 [1].

High impact information on npm-A

• Immunodepletion of XRIPalpha from the egg extracts blocks nuclear import of RPA but not that of nucleoplasmin, a classical import substrate [2].
• This indicates that it is not the synchronous action of both complexes which is required for nucleosome assembly, but that their cooperative action can be resolved into two steps: deposition of H3 and H4 from the N1/N2 complexes onto the DNA and completion of nucleosome core formation by addition of H2B and H2A from the nucleoplasmin complexes [3].
• While the histones from the N1/N2 complexes are efficiently transferred to DNA and induce supercoils into relaxed circular plasmid DNA, the nucleoplasmin complexes show no supercoil induction, but can also transfer their histones to DNA [3].
• Nucleoplasmin is the most abundant protein in the Xenopus oocyte nucleus [1].
• Nucleoplasmin cDNA sequence reveals polyglutamic acid tracts and a cluster of sequences homologous to putative nuclear localization signals [1].

Biological context of npm-A

• The different species observed most likely represent different levels of phosphorylation of nucleoplasmin [4].
• The amount of nucleoplasmin message present does not follow a similar pattern during oogenesis [4].

Anatomical context of npm-A

• Using nucleoplasmin-coated gold as a transport substrate, it was determined that the shift in synthesis from small to large RNAs during oogenesis is accompanied by an increase in both the rates of signal-mediated nuclear import and the functional size of nuclear pores [5].
• Using nucleoplasmin-coated colloidal gold particles to assay transport capacity, it was found that import was greatest at 1 h postanaphase (after complete reformation of the nuclear envelope) [6].

Associations of npm-A with chemical compounds

• Analysis of the stability and function of nucleoplasmin through cysteine mutants [7].
• To better understand the role of the three cysteines of nucleoplasmin on its pentameric functional structure, we have selectively mutated these residues to serine and generated three mutants (C15S, C35S, and C45S) both for the complete recombinant nucleoplasmin (r-NP) and the truncated r-NP142 non-tagged forms [7].

Other interactions of npm-A

• On addition of lambda DNA the immuno-depleted extract supported reconstitution of nuclei which were surrounded by a continuous double-membrane envelope but lacked pore complexes and were unable to import karyophilic proteins such as nucleoplasmin or lamin LIII [8].

Analytical, diagnostic and therapeutic context of npm-A

• Indirect immunofluorescence was used to study the temporal expression and spatial distribution of nucleoplasmin [4].
• Analysis of labelled oocyte proteins by two-dimensional immunoblots and autoradiography revealed that synthesis of nucleoplasmin was first detected in stage-2 oocytes, reached 60% maximum levels at stage 3, peaked at stage 4 and was undetectable in stage-6 oocytes [4].
• UV cross-linking of radiolabeled RNA to protein and immunoprecipitation of cross-linked proteins reveals an increased association of the chaperone nucleoplasmin with ribonucleoprotein particles dependent on the oocyte maturation process [9].
• RESULTS: In this work, the presence of nucleoplasmin in oocyte extracts from these three organisms has been assessed using Western Blotting [10].

References