Cellular Expression of Human Centromere Protein C Demonstrates a Cyclic Behavior with Highest Abundance in the G$_{1}$ Phase

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 93; no. 19; pp. 10234 - 10239
• Main Authors: Knehr, M., Poppe, M., Schroeter, D., Eickelbaum, W., E.-M. Finze, U.-L. Kiesewetter, Enulescu, M., Arand, M., Paweletz, N.
• Format: Journal Article
• Language: English
• Published: National Academy of Sciences of the United States of America 17.09.1996
• Subjects: Cell cycle; Cells; Complementary DNA; DNA; HeLa cells; Interphase; Kinetochores; Messenger RNA; Mitosis; Polymerase chain reaction
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.93.19.10234

Centromere proteins are localized within the centromere-kinetochore complex, which can be proven by means of immunofluorescence microscopy and immunoelectron microscopy. In consequence, their putative functions seem to be related exclusively to mitosis, namely to the interaction of the chromosomal kinetochores with spindle microtubules. However, electron microscopy using immune sera enriched with specific antibodies against human centromere protein C (CENP-C) showed that it occurs not only in mitosis but during the whole cell cycle. Therefore, we investigated the cell cycle-specific expression of CENP-C systematically on protein and mRNA levels applying HeLa cells synchronized in all cell cycle phases. Immunoblotting confirmed protein expression during the whole cell cycle and revealed an increase of CENP-C from the S phase through the G$_{2}$ phase and mitosis to highest abundance in the G$_{1}$ phase. Since this was rather surprising, we verified it by quantifying phase-specific mRNA levels of CENP-C, paralleled by the amplification of suitable internal standards, using the polymerase chain reaction. The results were in excellent agreement with abundant protein amounts and confirmed the cyclic behavior of CENP-C during the cell cycle. In consequence, we postulate that in addition to its role in mitosis, CENP-C has a further role in the G$_{1}$ phase that may be related to cell cycle control.