Overexpression of the ubiquitination/proteasome pathway. Interaction network analysis of the ubiquitination/proteasome pathway in the oocytes/hESC signature. (A) The interaction network was generated with the Ingenuity software and shows a high number of genes from this cellular pathway overexpressed (red) or expressed (orange) in the oocytes/hESC signature. Transcripts that were not detected by the microarray are white. Notably, we found elements of the ubiquitin-activating enzyme (UBE), BRCA1- and BRCA2-containing complex (BRCC), the regulatory 19S proteasome, the core proteolytic 20S proteasome and the ubiquitin-specific protease (USP) modules in the oocyte/hESC signature. Gene expression measured by microarrays in 9 genes involved in the ubiquitin and proteasome pathway (B). Box-and-whisker plots comparing the expression level of PSMA2, PSMA3, PSMA4, PSMA5, PSMC6, PSMD10, PSMD11, UBE2G1 and SKP2 in mature oocytes and hESC (38 samples) versus somatic tissues (167 samples). The signal intensity for each gene is shown on the y axis as arbitrary units determined by the GCOS 1.2 software (Affymetrix). (*): P-value < 0.0001 using a Mann-Whitney statistical test. Down regulation of the proteasome pathway during hESC differentiation (C). U133A microarray signal values for PSMA2, PSMA4 and PSMA5 in 29 undifferentiated hESC samples (mean value) versus two embryoid bodies (EB) samples (EB day 5 and EB day 14) and 3 non-lineage differentiated hESC samples (mean value).