Post-transcriptional fine-tuning of COP9 signalosome subunit biosynthesis is regulated by the c-Myc/Lin28B/let-7 pathway

ABSTRACT: The COP9 signalosome (CSN) is a conserved protein complex occurring in all eukaryotes. The mammalian CSN consists of eight subunits (CSN1 – CSN8) and possesses an intrinsic metalloprotease JAMM motif localised to CSN5. In addition, it is associated with kinases such as protein kinase CK2 and D and the ubiquitin (Ub) specific protease 15. It regulates cullin-RING Ub ligases (CRLs) that label proteins for proteolysis with poly-Ub chains in the Ub proteasome system (UPS). CRLs contain one of the scaffolding cullins 1 – 7, a RING domain protein e. g. Rbx1, and one of hundreds of substrate binding units such as F-box or BTB proteins that specifically target proteins for ubiquitination. The CSN forms functional supercomplexes with CRLs. It removes the Ub-like protein Nedd8 from cullins by its metalloprotease activity and thereby inactivates CRLs. On the other hand, it is essential for CRL function by protecting components and allowing reassembly of the complexes. As a regulator of the UPS the CSN is involved in cell cycle10, DNA repair and development. Overexpression of CSN subunits has been reported in tumour cells. Up to date nothing is known about CSN biogenesis and its regulation. Ten years ago we have observed that overexpression of selected CSN subunits caused a coordinated increase of all CSN subunits and a de novo biosynthesis of the entire complex. Here we show that overexpression of CSN1 mediates an increase of c-Myc which coordinates CSN subunit expression via microRNAs (miRNAs). miRNAs are evolutionarily conserved, endogenous, small, noncoding RNA molecules of about 22 nucleotides that function as posttranscriptional gene regulators. We found that inhibitors of let-7 family miRNAs or upregulation of c-Myc, which represses let-7 miRNAs, resulted in a coordinated increase of CSN subunits and de novo CSN biogenesis. Keywords: Gene expression analysis of human RNA samples using topic-defined PIQOR™ Ubiquitin-PS Microarrays. Two different platforms were used (these are two different microarray batches which are identical in terms of the spotted cDNAs, but differ in the position of some cDNAs) Gene expression analysis of Hela cells overexpressing either CSN2 or CSN1 was performed to study CSN biogenesis and its regulation. Curcumin, Nr. 8 (Curcumin analogon) and Piceatannol were used for the treatment of Hela cells since they inhibit the CSN associated kinases. The aim was to investigate the effect on the signalosome. For each treatment 50 µM Curcumin, Nr. 8 and Piceatannol were used.

ORGANISM(S): Homo sapiens

SUBMITTER: Silvia Rueberg 

PROVIDER: E-GEOD-19085 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress