Differentiation-specific nuclear matrix proteins cross-linked to DNA by cis-diammine dichloroplatinum

Co-localization of poly(ADPR)polymerase 1 (PARP-1) poly(ADPR)polymerase 2 (PARP-2) and related proteins in rat testis nuclear matrix defined by chemical cross-linking

Poly(ADPR)polymerase 1 and 2 (PARP-1, PARP-2) are nuclear enzymes which function is based on specific interactions with DNA and nuclear proteins. PARPs targets include proteins involved in DNA replication, repair, and transcription and their function can be modulated either by protein-protein interaction with native PARP-1 and by non-covalent interaction with poly(ADP-ribose) (pADPR) linked to the auto-modified PARP-1. Moreover, the association of pADPR and PARP-1 with the nuclear matrix (NM) has been reported, based on the poly(ADP-ribosyl)ation of nuclear matrix proteins (NMPs). In the present article, by the use of DNA and protein cross-linking reactions, by cis-diamminedichloroplatinum II (cDDP) and sodium tetrathionate (NaTT) respectively, we present more evidences about the association of PARP-1, PARP-2, and PARPs related proteins with the NM. Our findings confirmed that NM could be seen as a fraction greatly enriched in transcription factors (i.e., C/EBP-beta) and enzymes (DNA Topo II, DNA PK) that co-localize with PARP-1 and -2 at the matrix associated regions (MARs) of chromatin. Moreover, pADPR contributes to PARP-1 localization at the NM, showing that PARP(s) activity co-operates to the functions of this nuclear fraction.

Estrogen regulates the association of intermediate filament proteins with nuclear DNA in human breast cancer cells

In a previous study we showed that the levels of the intermediate filament proteins, cytokeratins 8, 18, and 19, in the nuclear matrix-intermediate filament (NM-IF) fraction from the hormone-dependent and estrogen receptor (ER)-positive human breast cancer cell line T-47D5 were regulated by estrogens. In contrast, estrogens did not regulate the cytokeratins in the NM-IF fraction of the hormone-independent and ER-positive cell line, T5-PRF. In this study, human breast cancer cells were treated with cis-diamminedichloroplatinum to cross-link protein to nuclear DNA in situ, and proteins bound to DNA were isolated. We show that cytokeratins 8, 18, and 19 of T-47D5 and T5-PRF were associated with nuclear DNA in situ. The levels of the cytokeratins 8, 18, and 19 bound to nuclear DNA or associated with the cytoskeleton of T-47D5 human breast cancer cells decreased when estrogens were depleted or the pure antiestrogen ICI 164,384 was added. In contrast, the cytokeratin levels associated with nuclear DNA or cytoskeleton were not significantly affected by estrogen withdrawal or antiestrogen administration in T5-PRF cells. These observations suggest that estrogen regulates the organization of nuclear DNA by rearrangement of the cytokeratin filament network in hormone-dependent, ER-positive human breast cancer cells and that this regulation is lost in hormone-independent, ER-positive breast cancer cells.