Casein kinase 2 (CK2) is a highly conserved phosphorylated serine/threonine kinase that is widely present in various eukaryotes and has a variety of physiological functions. CK2 holoenzymes are heterotetramers composed of two α catalytic subunits and two β regulatory subunits, but CK2 monomers can also independently perform certain physiological functions. Plant CK2 mostly belongs to the multi-gene family. CK2 is a typical multi-substrate protein kinase with hundreds of substrates. CK2 is vital to the viability of cells. In-depth research also gradually revealed that CK2 plays important physiological functions in the process of plant light-mediated gene expression regulation and flowering time control, physiological clock regulation, stress-resistance-related signaling pathways, and seed embryo development. In-depth study of the specific signaling pathways involved in CK2 and its regulatory mechanisms in plants is the key to understanding CK2 functions.
Casein kinase 2 (CK2) is a highly conserved phosphorylated serine/threonine kinase that is widely present in various eukaryotes and has multiple physiological functions. As the earliest identified protein kinase, there are hundreds of possible target sites in CK2, which are involved in many important physiological processes such as physiological clock, photoperiod and plant flower development, and regulation of ABA/stress-related gene expression. CK2 has some distinctive features. For example, CK2 is acidophilic, and its receptor is phosphorylated at the site containing multiple acidic amino acids. In addition to using ATP as a phosphate group for donors, GTP can also be used by CK2 to provide phosphate groups. CK2 It is not itself regulated by phosphorylation and is insensitive to all second messengers currently known. Although there are continuous new research results, there is still much work to be done to fully understand CK2 and its participation in physiological processes and specific physiological functions from a biochemical and genetic perspective, and little is known about the regulatory mechanism of CK2. Therefore, CK2 has always been one of the research interests of people.
As a highly conserved protein kinase that is widely present in animals, plants, and fungi, CK2 is critical to cell viability. CK2 is also involved in the cell cycle process in plants, but its role in determining cell fate has not been well studied. In plants, CK2 is involved in the regulation of gene expression in the light signal transduction pathway. HY5, an important member of the Arabidopsis light signal pathway, mainly plays a role in promoting the morphogenesis of light, is regulated by CK2, which can ensure that a certain amount of HY5 exists in a hyperphosphorylated state and is protected from degradation by the proteasome in the dark The activity makes HY5 work quickly after the night-day transition. There is increasing evidence that CK2 is involved in the regulation of the physiological clock. The circadian rhythm is maintained by the transcription feedback loop of the biological endogenous oscillator, but post-transcriptional regulation such as phosphorylation also plays a key role.
In substrate arrays that can be altered by CK2, many substrates have been found to increase the prevalence in breast, lung, colon, and prostate cancer. Increasing substrate concentrations in cancer cells may infer that the cells may have survival benefits, and that activation of many of these substrates requires CK2. The anti-apoptotic function of CK2 also enables cancer cells to escape cell death and continue to proliferate. The role of CK2 in cell cycle regulation that should be stopped under normal circumstances may also indicate the role of CK2 in allowing cell cycle progression. This also promotes CK2 as a possible therapeutic target for cancer drugs. When used in combination with other effective anticancer therapies, CK2 inhibitors can increase the effectiveness of other therapies by allowing drug-induced apoptosis to occur at a normal rate.
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