Biological activity and redistribution of nucleolar proteins of two different cell lines treated with cis-dichloro-1,2-propylenediamine-N,N,N',N'-tetraacetato ruthenium (III) (RAP).

The interaction of a newly synthesized antitumor complex cis-dichloro-1,2-propylenediamine-N,N,N',N'-tetraacetato ruthenium (III) (RAP) with DNA was investigated in vitro through a number of techniques including comet assay, immunoprecipitation, and immunolocalization of certain nucleolar proteins (the upstream binding factor (UBF) and fibrillarin) involved in DNA transcription, rRNA processing, and ribosomal assembly. The results showed that RAP binds to the DNA of two cell lines (H4 and Hs-683) causing a delay in cell proliferation rate leading to a number of cellular modifications. These modifications include DNA-damage assessed by the single cell gel electrophoresis method (comet assay) and variation in the expression of nucleolar proteins; UBF was more abundant in RAP treated cells, this was explained by the high affinity of this protein to DNA modified by RAP. On the other hand, fibrillarin was found in less quantities in RAP treated cells which was explained by a de-regulation of the ribosomal machinery caused by RAP.

In vitro expression and redistribution of nucleolar proteins following the treatment with cis-dichloro-1,2-propylenediamine-N,N,N',N'-tetraacetato ruthenium (III) (RAP).

In this study, we used a newly synthesized antitumor complex [RuLCl2]H.4H2O (RAP), having the same antitumor effects as cisplatin but showing lower cytotoxicity. We found that RAP-DNA adducts induce a high expression of proteins with high molecular weight and a low expression of proteins with low molecular weight. We choose two proteins: the upstream binding factor (UBF), an RNA polymerase I-specific transcription factor that recognizes the ribosomal RNA gene promoter and initiates transcription; and fibrillarin, which is involved in many posttranscriptional processes including pre-rRNA processing, pre-rRNA methylation, and ribosome assembly. Our results showed that UBF was present in high quantities in TG cell extracts treated with RAP with a major abundance of UBF1 more than UBF2, which was explained by a high affinity of UBF1 for DNA modified by RAP than UBF2; while fibrillarin was present in low quantities in protein extracts treated with RAP. Also, following treatment with RAP, there was a similar redistribution of UBF along the nucleus of TG cells as in the controls but with the presence of higher quantities of this factor in the nucleoplasm, which could be explained by an increase of the UBF affinity for the no nucleolar chromatin as a consequence of the modifications induced by RAP. Fibrillarin was found in low quantities in the fibrillar centers and in the nucleoplasm after treatment with RAP.