title: Proliferation marker pKi-67 affects the cell cycle in a self-regulated manner.
abstract: The proliferation marker pKi-67 is commonly used in research and pathology to detect proliferating cells. In a previous work, we found the protein to be associated with regulators of the cell cycle, controlling S-phase progression, as well as entry into and exit from mitosis. Here we investigate whether pKi-67 has a regulative effect on the cell cycle itself. For that purpose we cloned four fragments of pKi-67, together representing nearly the whole protein, and an N-terminal pKi-67 antisense oligonucleotide into a tetracycline inducible gene expression system. The sense fragments were C-terminally modified by addition of either a nuclear localization sequence (NLS) or a STOP codon to address the impact of their intracellular distribution. FACS based cell cycle analysis revealed that expression of nearly all pKi-67 domains and the antisense oligonucleotide led to a decreased amount of cells in S-phase and an increased number of cells in G(2)/M- and G(1)-phase. Subsequent analysis of the endogenous pKi-67 mRNA and protein levels revealed that the constructs with the most significant impact on the cell cycle were able to silence pKi-67 transcription as well. We conclude from the data that pKi-67 influences progression of S-phase and mitosis in a self-regulated manner and, therefore, effects the cell cycle checkpoints within both phases. Furthermore, we found pKi-67 mediates an anti-apoptotic effect on the cell and we verified that this marker, although it is a potential ribosomal catalyst, is not expressed in differentiated tissues with a high transcriptional activity.
authors.affiliation: Surgical Research Laboratory, University of Lübeck, Lübeck, Germany.
authors.forename: Mirko H H
authors.initials: MH
authors.lastname: Schmidt
authors.forename: Rainer
authors.initials: R
authors.lastname: Broll
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Bruch
authors.forename: Michael
authors.initials: M
authors.lastname: Duchrow
mesh_terms: D000974:Antibodies, Antinuclear / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects* / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology; D003106:Colon / Q000166:cytology; D015870:Gene Expression; D020397:Goblet Cells / Q000166:cytology / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D019394:Ki-67 Antigen / Q000235:genetics / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D010179:Pancreas / Q000166:cytology; D010446:Peptide Fragments / Q000235:genetics / Q000494:pharmacology; D010525:Peripheral Nerves / Q000166:cytology; D010950:Plasma Cells / Q000166:cytology / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000494:pharmacology; D012097:Repressor Proteins / Q000235:genetics; D013194:Staining and Labeling; D013752:Tetracycline; D014162:Transfection
chemical_list: D000974:Antibodies, Antinuclear; D000911:Antibodies, Monoclonal; D019394:Ki-67 Antigen; D010446:Peptide Fragments; D011994:Recombinant Proteins; D012097:Repressor Proteins; C034811:tetracycline resistance-encoding transposon repressor protein; D013752:Tetracycline