Lipin1 Regulates Skeletal Muscle Differentiation through Extracellular Signal-regulated Kinase (ERK) Activation and Cyclin D Complex-regulated Cell Cycle Withdrawal

The extracellular signal-regulated kinase (ERK) pathway is generally mitogenic, but, upon strong activation, it causes cell cycle arrest by a not-yet fully understood mechanism. In response to genotoxic stress, Chk1 hyperphosphorylates Cdc25A, a positive cell cycle regulator, and targets it for Skp1/Cullin1/F-box protein (SCF)β-TrCP ubiquitin ligase-dependent degradation, thereby leading to cell cycle arrest. Here, we show that strong ERK activation can also phosphorylate and target Cdc25A for SCFβ-TrCP-dependent degradation. When strongly activated in Xenopus eggs, the ERK pathway induces prominent phosphorylation and SCFβ-TrCP-dependent degradation of Cdc25A. p90rsk, the kinase downstream of ERK, directly phosphorylates Cdc25A on multiple sites, which, interestingly, overlap with Chk1 phosphorylation sites. Furthermore, ERK itself phosphorylates Cdc25A on multiple sites, a major site of which apparently is phosphorylated by cyclin-dependent kinase (Cdk) in Chk1-induced degradation. p90rsk phosphorylation and ERK phosphorylation contribute, roughly equally and additively, to the degradation of Cdc25A, and such Cdc25A degradation occurs during oocyte maturation in which the endogenous ERK pathway is fully activated. Finally, and importantly, ERK-induced Cdc25A degradation can elicit cell cycle arrest in early embryos. These results suggest that strong ERK activation can target Cdc25A for degradation in a manner similar to, but independent of, Chk1 for cell cycle arrest.

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Skeletal muscle cells lacking the retinoblastoma protein display defects in muscle gene expression and accumulate in S and G2 phases of the cell cycle.

The Journal of Cell Biology ◽

10.1083/jcb.135.2.441 ◽

1996 ◽

Vol 135 (2) ◽

pp. 441-456 ◽

Cited By ~ 206

Author(s):

B G Novitch ◽

G J Mulligan ◽

T Jacks ◽

A B Lassar

Keyword(s):

Cell Cycle ◽

Skeletal Muscle ◽

Cell Cycle Progression ◽

Muscle Differentiation ◽

Mitotic Catastrophe ◽

Skeletal Muscle Differentiation ◽

Differentiation Markers ◽

Muscle Gene Expression ◽

Retinoblastoma Tumor ◽

Muscle Gene

Viral oncoproteins that inactivate the retinoblastoma tumor suppressor protein (pRb) family both block skeletal muscle differentiation and promote cell cycle progression. To clarify the dependence of terminal differentiation on the presence of the different pRb-related proteins, we have studied myogenesis using isogenic primary fibroblasts derived from mouse embryos individually deficient for pRb, p107, or p130. When ectopically expressed in fibroblasts lacking pRb, MyoD induces an aberrant skeletal muscle differentiation program characterized by normal expression of early differentiation markers such as myogenin and p21, but attenuated expression of late differentiation markers such as myosin heavy chain (MHC). Similar defects in MHC expression were not observed in cells lacking either p107 or p130, indicating that the defect is specific to the loss of pRb. In contrast to wild-type, p107-deficient, or p130-deficient differentiated myocytes that are permanently withdrawn from the cell cycle, differentiated myocytes lacking pRb accumulate in S and G2 phases and express extremely high levels of cyclins A and B, cyclin-dependent kinase (Cdk2), and Cdc2, but fail to readily proceed to mitosis. Administration of caffeine, an agent that removes inhibitory phosphorylations on inactive Cdc2/cyclin B complexes, specifically induced mitotic catastrophe in pRb-deficient myocytes, consistent with the observation that the majority of pRb-deficient myocytes arrest in S and G2. Together, these findings indicate that pRb is required for the expression of late skeletal muscle differentiation markers and for the inhibition of DNA synthesis, but that a pRb-independent mechanism restricts entry of differentiated myocytes into mitosis.

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Intercellular propagation of extracellular signal-regulated kinase activation revealed by in vivo imaging of mouse skin

eLife ◽

10.7554/elife.05178 ◽

2015 ◽

Vol 4 ◽

Cited By ~ 94

Author(s):

Toru Hiratsuka ◽

Yoshihisa Fujita ◽

Honda Naoki ◽

Kazuhiro Aoki ◽

Yuji Kamioka ◽

...

Keyword(s):

Cell Cycle ◽

Cell Cycle Progression ◽

Mouse Skin ◽

Egf Receptors ◽

M Cell ◽

Erk Activation ◽

Extracellular Signal Regulated Kinase ◽

Extracellular Signal ◽

Erk Activity

Extracellular signal-regulated kinase (ERK) is a key effector of many growth signalling pathways. In this study, we visualise epidermal ERK activity in living mice using an ERK FRET biosensor. Under steady-state conditions, the epidermis occasionally revealed bursts of ERK activation patterns where ERK activity radially propagated from cell to cell. The frequency of this spatial propagation of radial ERK activity distribution (SPREAD) correlated with the rate of epidermal cell division. SPREADs and proliferation were stimulated by 12-O-tetradecanoylphorbol 13-acetate (TPA) in a manner dependent on EGF receptors and their cognate ligands. At the wounded skin, ERK activation propagated as trigger wave in parallel to the wound edge, suggesting that ERK activation propagation can be superimposed. Furthermore, by visualising the cell cycle, we found that SPREADs were associated with G2/M cell cycle progression. Our results provide new insights into how cell proliferation and transient ERK activity are synchronised in a living tissue.

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The Bromodomains of the mammalian SWI/SNF (mSWI/SNF) ATPases Brahma (BRM) and Brahma Related Gene 1 (BRG1) promote chromatin interaction and are critical for skeletal muscle differentiation

10.1101/2020.08.25.267666 ◽

2020 ◽

Author(s):

Tapan Sharma ◽

Hanna Witwicka ◽

Anthony N. Imbalzano

Keyword(s):

Gene Expression ◽

Cell Cycle ◽

Skeletal Muscle ◽

Muscle Differentiation ◽

Chromatin Interaction ◽

Specific Gene ◽

Gene Promoters ◽

Skeletal Muscle Differentiation ◽

Chromatin Binding ◽

Chip Analysis

ABSTRACTSkeletal muscle differentiation induces changes in the epigenome of myoblasts as they proceed towards a myogenic phenotype. mSWI/SNF chromatin remodeling enzymes coordinate with lineage-determining transcription factors and are key regulators of differentiation. Three mSWI/SNF proteins, the mutually exclusive ATPases, BRG1 and BRM, and the BAF180 protein (Polybromo1, PBRM1) contain bromodomains belonging to the same structural subfamily. Bromodomains bind to acetylated lysines on histone N-terminal tails and on other proteins. Pharmacological inhibition of mSWI/SNF bromodomain function using the selective inhibitor PFI-3 reduced differentiation, decreased expression of myogenic genes, and increased the expression of cell cycle-related genes, and the number of cells that remained in the cell cycle. Knockdown of BAF180 had no effect on differentiation, suggesting that only the BRG1 and BRM bromodomains contributed to differentiation. Comparison with existing gene expression data from myoblasts subjected to knockdown of BRG1 or BRM showed that bromodomain function was required for a subset of BRG1- and BRM-dependent gene expression. ChIP analysis revealed decreased BRG1 and BRM binding to target gene promoters, indicating that the BRG1 and BRM bromodomains promote chromatin binding. Thus mSWI/SNF ATPase bromodomains contribute to cell cycle exit, to skeletal muscle-specific gene expression, and to stable promoter binding by the mSWI/SNF ATPases.

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