repp86 : Regulation und Interaktion mit Proteinen
repp86, the "restrictedly expressed proliferation associated protein with 86 kDa molecular weight" is specifically regulated in a cell cycle-dependent manner. repp86 is exclusively expressed in proliferating cells from the transition G1/S until the end of cytokinesis. During mitosis repp86 becomes highly phosphorylated and associates with spindle poles and the spindle apparatus. The regulation of repp86-expression in quiescent cells occurs at the transcriptional level. repp86-overexpressing human HEK293 cells become polyploid and undergo cell cycle arrest in G2/M phase. repp86-transfected COS7 cells become multinucleated and contain malformed polymorphous nuclei suggesting a role of repp86 in chromosome segregation. repp86 binds to microtubules in vitro and interacts with SIAH2, an ubiquitin ligase. Ubiquitination of repp86 probably targets the protein for proteasomal degradation. The 5'-transcript leader includes an upsteam open reading frame coding for 14 amino acids. The absolutely essential promoter fragment matches to the DNA region between the nucleotides +22 and +92 including binding sites for c-ETS-1 and NRF2.