Down-regulation of CK2α correlates with decreased expression levels of DNA replication minichromosome maintenance protein complex (MCM) genes

Abstract

Protein kinase CK2 is a serine/threonine kinase composed of two catalytic subunits (CK2α and/or CK2α’) and two regulatory subunits (CK2β). It is implicated in every stage of the cell cycle and in the regulation of various intracellular pathways associated with health and disease states. The catalytic subunits have similar biochemical activity, however, their functions may differ significantly in cells and in vivo. In this regard, homozygous deletion of CK2α leads to embryonic lethality in mid-gestation potentially due to severely impaired cell proliferation. To determine the CK2α-dependent molecular mechanisms that control cell proliferation, we established a myoblast-derived cell line with inducible silencing of CK2α and carried out a comprehensive RNA-Seq analysis of gene expression. We report evidence that CK2α depletion causes delayed cell cycle progression through the S-phase and defective response to replication stress. Differential gene expression analysis revealed that the down-regulated genes were enriched in pathways implicated in cell cycle regulation, DNA replication and DNA damage repair. Interestingly, the genes coding for the minichromosome maintenance proteins (MCMs), which constitute the core of the replication origin recognition complex, were among the most significantly down-regulated genes. These findings were validated in cells and whole mouse embryos. Taken together, our study provides new evidence for a critical role of protein kinase CK2 in controlling DNA replication initiation and the expression levels of replicative DNA helicases, which ensure maintenance of proliferative potential and genome integrity in eukaryotic cells.

Down-Regulation of CK2α Leads toUp-Regulation of the Cyclin-Dependent Kinase Inhibitor p27KIP1 in Conditions Unfavorable for the Growth of Myoblast Cells

“…1 demonstrated that lack of CK2α induces significant inhibition of cell growth and delayed transition through G1 and/or to S phase. This is consistent with our previous findings [20]. Furthermore, doxycycline did not show any significant effect on the parental cell line (i.e.…”

“…An important observation that emerged from the study is that lowered expression levels of CK2α resulted in decreased cell proliferation and a significant slightly increased G1 population over the course of several days. However, unlike cancer cells, reduced cell proliferation was not accompanied by increased cell death either in vivo or in vitro [20].…”

“…Immunological analysis of mouse tissue sections was performed essentially as described in [20]. Detection of p27 KIP1 was carried out staining three somite-paired WT and CK2α-/-embryos (KO) with rabbit polyclonal anti-p27 KIP1 (Thermo Fisher Scientific).…”

“…Earlier work in our laboratory showed that myoblasts with down-regulation of CK2α proliferate more slowly and display an increase in the fraction of cells in G1 as compared to the parental cells [20]. To further investigate this, we used the IncuCyte S3 live-cell imaging system to measure cell proliferation employing a real-time kinetic platform.…”

“…We have recently established a myoblast cell line (hereafter referred to as H9c2-CK2α-44) derived from rat heart tissue with the ability to induce down-regulation of CK2α by a doxycycline-inducible shRNA [20]. An important observation that emerged from the study is that lowered expression levels of CK2α resulted in decreased cell proliferation and a significant slightly increased G1 population over the course of several days.…”