F The recombinant UBE2S ER/ER variant increases Cyclin B degradation in G1 extracts compared to UBE2S wild-type (WT), monitored by immunoblot. G1 extracts were prepared from HeLa S3 cells treated with either control firefly luciferase siRNA (siFF) or two UBE2S siRNAs (siUBE2S). 