In Vitro Expression and Redistribution of Nucleolar Proteins Following the Treatment With <I>cis</I>-Dichloro-1,2-propylenediamine-<I>N,N,N′,N′</I>-tetraacetato Ruthenium (III) (RAP)

Abstract

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.