Solubility partitioning of C/EBPbeta on the rat hepatocyte nuclear matrix by hydrophobic interactions.

Authors: Uskokovic, A  Vidakovic, M  Dinic, S  Ivanovic-Maticc, S  Martinovic, V  Poznanovic, G 
Citation: Uskokovic A, etal., Cell Biol Int. 2002;26(5):451-61.
Pubmed: (View Article at PubMed) PMID:12095231
DOI: Full-text: DOI:10.1006/cbir.2002.0888

The greatest part of nuclear C/EBPbeta (a major 35 kD protein, 30 and 38 kD isoforms) was observed to partition with the nuclear matrix. Cross-linking experiments with formaldehyde suggested that the association reflected the in situ juxtapositioning of C/EBPbeta to nuclear matrix proteins in isolated nuclei. The association of C/EBPbeta with the nuclear matrix resisted RNase and DNase treatment and extraction with protein sulfhydryl reducing agents combined with high ionic strength salt. C/EBPbeta displayed a proclivity to extensively reassemble with the filament-forming nuclear matrix proteins after a cycle of solubilization with urea, followed by its removal by dialysis. These findings suggest that the C/EBPbeta moieties were anchored to the nuclear matrix through hydrophobic protein-protein interactions with the lamins. Subsequent separation of nuclear matrix-associated C/EBPbeta into insoluble, reassembling, and soluble nuclear matrix protein (SNMP) fractions after a cycle of solubilization/reassembly pointed to the sub-partitioning of C/EBPbeta on the nuclear matrix. DNA affinity chromatography using the rat haptoglobin gene cis -element and SNMP revealed the binding of p35 during basal transcription, and p35 and p30 during elevated haptoglobin gene transcription in the course of the acute-phase (AP) response. It was concluded that the appearance of cis -element-binding p30 in the SNMP fraction resulted from its increased solubility (decreased hydrophobicity) and inability to reassociate with the lamins during urea removal. The observed solubility partitioning of C/EBPbeta on the nuclear matrix framework could represent a level of control of the general availability of regulatory proteins for establishing interactions with DNA.

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CRRD ID: 2303386
Created: 2009-02-10
Species: All species
Last Modified: 2009-02-10
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.