Background: The COP9 signalosome (CSN) is a conserved protein complex in eukaryotic cells consisting of eight subunits (CSN1 to CSN8). Recent data demonstrate that the CSN is a regulator of the ubiquitin (Ub) proteasome system (UPS). It controls substrate ubiquitination by cullin-RING Ub ligases (CRLs), a process that determines substrate specificity of the UPS. The intrinsic deneddylating activity localized to CSN5 as well as the associated kinases and deubiquitinating activity are involved in the regulatory function of CSN. The exact mechanisms are unclear. In this study we knocked down CSN1 (siCSN1), CSN3 (siCSN3) and CSN5 (siCSN5) by specific siRNA oligos permanently expressed in HeLa cells. The analysis and comparison of siRNA cells revealed differential impact of individual subunits on CSN structure and function.

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The diagnostic specificity of the detection of disseminated prostatic cells by reverse-transcriptase polymerase chain reaction (RT-PCR) of PSA mRNA was investigated. A sensitive nested PCR was developed. In blood samples from 10 healthy female and 10 healthy male persons examined by RT-PCR, mRNA of PSA was detected 3 times in each group. In the groups of patients suffering from benign prostate hyperplasia and prostate cancer, 6 of 11 and 5 of 12, respectively, gave positive RT-PCR results. With increasing analytical sensitivity of the RT-PCR of PSA mRNA, the diagnostic specificity of the assay is decreased. Further development of this diagnostic method requires the introduction of the quantitative PCR which may make possible discrimination between prostatic and non-prostatic source of PSA mRNA by quantification. Int.