Rapid turnover of cell‐cycle regulators found in Mirk/dyrk1B transfectants

Ewton, Daina Z.; Lee, Kangmoon; Deng, Xiaobing; Lim, Seunghwan; Friedman, Eileen

doi:10.1002/ijc.10743

Cited by 28 publications

(20 citation statements)

References 34 publications

(55 reference statements)

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“…8) with only a 20% decrease in p27 mRNA levels (not shown). The minimal effect of Mirk on p27 mRNA levels was also seen by microarray analysis (data not shown) and confirmed our earlier results (21), which showed that Mirk did not modulate the activity of a p27 promoter construct. These data indicated that Mirk plays a post-translational role in maintaining p27 stability in post-mitotic myoblasts as well as NIH3T3 cells.…”

Section: Figsupporting

confidence: 91%

The Cyclin-dependent Kinase Inhibitor p27Kip1 Is Stabilized in G0 by Mirk/dyrk1B Kinase

Deng

Mercer

Shah

et al. 2004

Journal of Biological Chemistry

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Section: Figsupporting

confidence: 91%

The Cyclin-dependent Kinase Inhibitor p27Kip1 Is Stabilized in G0 by Mirk/dyrk1B Kinase

Deng

Mercer

Shah

et al. 2004

Journal of Biological Chemistry

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125

156

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“…3E), accounting for the increased protein abundance. In earlier studies, stable Mirk transfectants of colon cancer cells were shown to exhibit a faster turnover of cyclin D1 (20). Thus, both Mirk depletion (this study) and Mirk overexpression studies showed that Mirk destabilized cyclin D isoforms in colon cancer cells.…”

Section: Mirk Depletion Leads To a Rapid Transit Of G1 In Colon Cancesupporting

confidence: 58%

Mirk Regulates the Exit of Colon Cancer Cells from Quiescence

Jin

Ewton

Park

et al. 2009

Journal of Biological Chemistry

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Mirk/Dyrk1B is a serine/threonine kinase widely expressed in colon cancers. Serum starvation induced HD6 colon carcinoma cells to enter a quiescent G0 state, characterized by a 2N DNA content and a lower RNA content than G1 cells. Compared with cycling cells, quiescent cells exhibited 16-fold higher levels of the retinoblastoma protein p130/Rb2, which sequesters E2F4 to block entry into G1, 10-fold elevated levels of the CDK inhibitor p27kip1, and 10-fold higher levels of Mirk. However, depletion of Mirk did not prevent entry into G0, but enabled quiescent HD6, SW480, and colo320 colon carcinoma cells to acquire some biochemical characteristics of G1 cells, including increased levels of cyclin D1 and cyclin D3 because of slower turnover, increased activity of their CDK4/cyclin D complexes, and increased phosphorylation and decreased E2F4 sequestering ability of the CDK4 target, p130/Rb2. As a result, depletion of Mirk allowed some cells to escape quiescence and enabled cells released from quiescence to traverse G1 more quickly. The kinase activity of Mirk was increased by the chemotherapeutic drug 5-fluorouracil (5-FU). Treatment of p53 mutant colon cancer cells with 5-FU led to an elongated G1 in a Mirk-dependent manner, as G1 was shortened by ectopic overexpression of cyclin D1 mutated at the Mirk phosphorylation site (T288A), but not by wild-type cyclin D1. Mirk, through regulating cyclin D turnover, and the CDK inhibitor p27, as shown by depletion studies, functioned independently and additively to regulate the exit of tumor cells from quiescence.Solitary disseminated tumor cells that are negative for proliferation markers such as Ki67 are thought to be the source of tumor recurrence. These dormant tumor cells are quiescent, reversibly arrested in the G0 part of the cell cycle, and can reenter the cell cycle under favorable clues from the microenvironment. Quiescence is not simply a long G1 period, but is characterized by specific changes in gene expression (1). Factors that allow the prolonged survival of quiescent tumor cells in vivo are of clinical relevance and include antioxidant proteins. A requirement for quiescence in normal hematopoietic stem cells is repression of the production of reactive oxygen species (ROS) 2 (2), making it likely that cancer cells also require low ROS levels to maintain quiescence. The serine/threonine kinase Mirk was recently shown to reduce ROS levels in two pancreatic cancer cell lines by increasing transcription of a cohort of genes that detoxify superoxides and prevent the generation of hydroxyl radicals (3). The ROS-countering activity of Mirk was primarily exhibited in quiescent tumor cells because such cells had the highest levels of Mirk protein. Thus Mirk maintains the viability of quiescent pancreatic cancer cells through up-regulating antioxidant genes. Mirk/Dyrk1B is a member of a conserved family of serine/ threonine kinases that are activated by intramolecular tyrosine phosphorylation and which mediate maturation in different tissues: Mirk in skeletal muscle, Dy...

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“…In an earlier study, we had observed that stable overexpression of Mirk in colon carcinoma cells enhanced the turnover of cyclin D1 and the CDK inhibitor p27kip1 (25). These results appeared contradictory and may have resulted from the changes in cell physiology that occur in the presence of elevated expression of an active kinase with many potential cellular targets.…”

Section: Discussionmentioning

confidence: 96%

Mirk/dyrk1B Kinase Destabilizes Cyclin D1 by Phosphorylation at Threonine 288

Zou

Ewton

Deng

et al. 2004

Journal of Biological Chemistry

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The phosphorylation of cyclin D1 at threonine 286 by glycogen synthase kinase 3␤ (GSK3␤) has been shown to be required for the ubiquitination and nuclear export of cyclin D1 and its subsequent degradation in the proteasome. The mutation of the nearby residue, threonine 288, to nonphosphorylatable alanine has also been shown to reduce the ubiquitination of cyclin D1, suggesting that phosphorylation at threonine 288 may also lead to degradation of cyclin D1. We now demonstrate that the G 0 /G 1 -active arginine-directed protein kinase Mirk/dyrk1B binds to cyclin D1 and phosphorylates cyclin D1 at threonine 288 in vivo and that the cyclin D1-T288A construct is more stable than wild-type cyclin Cell cycle progression in eukaryotic cells is mediated by cyclin-dependent kinases (CDKs). 1 The D-type cyclins, D1, D2, and D3, increase in nuclear abundance in G 1 in response to mitogens, facilitate the import of CDK4 into the nucleus (1), and assemble combinatorially with CDK4 or CDK6 into complexes that phosphorylate the retinoblastoma protein, releasing factors needed for the progression into S phase. Cyclin D1 is translocated into the cytoplasm during S phase where it is destroyed by the proteasome following phosphorylation at threonine 286 by GSK3␤ (2, 3). Mutant cyclin D1-T286A, which cannot be phosphorylated by GSK3␤, is stabilized in the nucleus and is capable of transforming murine fibroblasts, whereas overexpression of wild-type cyclin D1 cannot act alone to transform such cells (4). A cyclin D1 isoform derived by alternative splicing was shown to lack threonine 286, enabling this cyclin D1 isoform to remain nuclear throughout the cell cycle, remain highly expressed, and function to facilitate transformation of NIH3T3 cells (5). This cyclin D1 splice variant was also found in tumor-derived cells and primary human esophageal tumors (5). Overexpression of cyclin D1 occurs in several cancers including breast, pancreatic, and esophageal (6), suggesting that either increased transcription, transcription of stable splice variants, or dysregulation of cyclin D1 turnover may frequently occur in cancer.In this study, we have studied the interaction of the ubiquitously expressed protein kinase Mirk/dyrk1B with cyclin D1. Mirk/dyrk1B is an arginine-directed serine/threonine kinase (7), which functions as a transcriptional co-activator and is activated through the stress-activated mitogen-activated protein kinase kinase MKK3 (8). We have shown recently that Mirk stabilizes the CDK inhibitor p27kip1 in the G 0 phase of the cell cycle in NIH3T3 fibroblasts, whereas depletion of Mirk by RNA interference increases cell cycling as measured by increased PCNA expression (9). Mirk expression is decreased by mitogen activation of the MEK-ERK pathway during G 1 (10), restricting Mirk function primarily to G 0 and early G 1 . We now confirm that transient overexpression of Mirk in nontransformed Mv1Lu lung epithelial cells increases the length of G 0 /G 1 by FACS analysis and that Mirk targets the G 1 cell cycle regulator, cyclin D1, t...

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Rapid turnover of cell‐cycle regulators found in Mirk/dyrk1B transfectants

Cited by 28 publications

References 34 publications

The Cyclin-dependent Kinase Inhibitor p27Kip1 Is Stabilized in G0 by Mirk/dyrk1B Kinase

The Cyclin-dependent Kinase Inhibitor p27Kip1 Is Stabilized in G0 by Mirk/dyrk1B Kinase

Mirk Regulates the Exit of Colon Cancer Cells from Quiescence

Mirk/dyrk1B Kinase Destabilizes Cyclin D1 by Phosphorylation at Threonine 288

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