Cdk6 blocks myeloid differentiation by interfering with Runx1 DNA binding and Runx1-C/EBPα interaction

Fujimoto, Toru; Km, Anderson; Jacobsen, Sten Eirik W.; Nishikawa, Sadakatsu; Nerlov, Claus

doi:10.1038/sj.emboj.7601675

“…Moreover, there is mounting evidence for a specific role for Cdk6 in differentiation, especially in neuronal and haematopoietic cells (Ericson et al, 2003;Slomiany et al, 2006;Fujimoto et al, 2007;Grossel and Hinds, 2006;Matushansky et al, 2003). These studies support the idea that the G1 Cdks have overlapping, yet distinct, activities.…”

supporting

confidence: 73%

Knockdown of Fbxo7 reveals its regulatory role in proliferation and differentiation of haematopoietic precursor cells

Meziane¹,

Randle²,

Nelson³

et al. 2011

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Research Article 2175 IntroductionDuring the cell cycle, ubiquitin-mediated proteolysis provides a swift and precise means to regulate the abundance of cell cycle regulatory proteins, including cyclins and cyclin-dependent kinase (Cdk) inhibitors. This mechanism for regulating the turnover of proteins is mediated through ubiquitin ligases, which transfer ubiquitin to target proteins, enabling their timely destruction (Hershko, 1997;Hershko and Ciechanover, 1998;Nakayama and Nakayama, 2006;Reed, 2006;Reed, 2003). E3 ubiquitin-ligases promote the specific attachment of poly-ubiquitin chains, which then triggers proteolysis by the 26S proteasome. SCF-type (Skp1-Cullin-F-box) E3 ubiquitin ligases are multi-subunit complexes that consisting of Skp1, Cullin, Rbx1 and an F-box protein (FBP) (Ang and Wade, 2005;Deshaies, 1999;Jackson and Eldridge, 2002;Nakayama and Nakayama, 2005;Vodermaier, 2004). It is the FBP, which has a crucial role in specifically recruiting the target substrate, usually directed by post-translational modification of the substrate (Cenciarelli et al., 1999;Hermand, 2006;Ho et al., 2008;Jin et al., 2004;Winston et al., 1999). In cell cycle regulation, several FBPs that regulate G1-S phase regulators have been intensively studied. These include the prototypical S-phase kinaseassociated protein 2 (Skp2, also known as Fbxl1) and the F-box and WD repeat domain containing 7 (Fbxw7) that, respectively, regulate the levels of the Cdk inhibitors cyclin E and cyclindependent kinase inhibitor 1B (CDKN1B; also known as and hereafter referred to as p27). In addition, three FBPs -Fbxo4, Another FBP that interacts with G1-S regulatory proteins is Fbox protein 7 (Fbxo7). In contrast to the destabilising effects of other FBPs, Fbxo7 acts as a specific assembly factor for cyclin DCdk6 complexes. Fbxo7 interacts directly with both Cdk6 and p27, and cooperatively increases cyclin D3 interactions with Cdk6 in vitro (Laman et al., 2005). In vivo, Fbxo7 overexpression in immortalised murine fibroblasts leads to their Cdk6-dependent transformation. These cells had increased levels of cyclin D-Cdk6 complexes and E2F activity, and formed tumours in athymic nude mice (Laman et al., 2005). Many mitogen and cytokine signalling pathways converge on cyclin D-Cdk activity, which -when overstimulated -promotes oncogenesis. Because of its Cdk6-dependent transforming activity, we propose that Fbxo7 functions as an oncogene.In U2OS and NIH3T3 cells, Fbxo7 has shown selectivity for Cdk6 over Cdk2 and Cdk4. Although the biochemical properties of Cdk4 and Cdk6 are similar, more-recent studies have indicated that differences can be discerned in their selective binding to cofactors (Sugimoto et al., 1999;Laman et al., 2005), preference for phosphorylation sites in pRb in vitro (Takaki et al., 2005), sensitivities to INK4 family members (Tourigny et al., 2002;Jones et al., 2007) and in vivo partnering with D-type cyclins (Ely et al., 2005). Also, in studies of knockout mice, tissue-specific defects are seen: Cdk4-knockout mice have impair...

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“…How cell cycle regulatory proteins like Fbxo7 and Cdk6 influence differentiation and cell cycle, and at which maturation stage this occurs is an interesting question for future study. There are experimental data that indicate direct binding of Cdk6 to transcription factors that regulate differentiation, suggesting a cellcycle-independent function (Fujimoto et al, 2007), whereas other studies show that downregulation of Cdk6 protein is crucial for terminal differentiation, presumably by allowing a permanent withdrawal from the cell cycle (Matushansky et al, 2003). In addition, it is possible that these proteins have different regulatory roles, cell cycle and/or transcriptional functions at different times in cell maturation.…”

Section: Discussionmentioning

confidence: 96%

Knockdown of Fbxo7 reveals its regulatory role in proliferation and differentiation of haematopoietic precursor cells

Meziane

¹

,

Randle

²

,

Nelson

³

et al. 2011

Journal of Cell Science

View full text Add to dashboard Cite

Research Article 2175 IntroductionDuring the cell cycle, ubiquitin-mediated proteolysis provides a swift and precise means to regulate the abundance of cell cycle regulatory proteins, including cyclins and cyclin-dependent kinase (Cdk) inhibitors. This mechanism for regulating the turnover of proteins is mediated through ubiquitin ligases, which transfer ubiquitin to target proteins, enabling their timely destruction (Hershko, 1997;Hershko and Ciechanover, 1998;Nakayama and Nakayama, 2006;Reed, 2006;Reed, 2003). E3 ubiquitin-ligases promote the specific attachment of poly-ubiquitin chains, which then triggers proteolysis by the 26S proteasome. SCF-type (Skp1-Cullin-F-box) E3 ubiquitin ligases are multi-subunit complexes that consisting of Skp1, Cullin, Rbx1 and an F-box protein (FBP) (Ang and Wade, 2005;Deshaies, 1999;Jackson and Eldridge, 2002;Nakayama and Nakayama, 2005;Vodermaier, 2004). It is the FBP, which has a crucial role in specifically recruiting the target substrate, usually directed by post-translational modification of the substrate (Cenciarelli et al., 1999;Hermand, 2006;Ho et al., 2008;Jin et al., 2004;Winston et al., 1999). In cell cycle regulation, several FBPs that regulate G1-S phase regulators have been intensively studied. These include the prototypical S-phase kinaseassociated protein 2 (Skp2, also known as Fbxl1) and the F-box and WD repeat domain containing 7 (Fbxw7) that, respectively, regulate the levels of the Cdk inhibitors cyclin E and cyclindependent kinase inhibitor 1B (CDKN1B; also known as and hereafter referred to as p27). In addition, three FBPs -Fbxo4, Another FBP that interacts with G1-S regulatory proteins is Fbox protein 7 (Fbxo7). In contrast to the destabilising effects of other FBPs, Fbxo7 acts as a specific assembly factor for cyclin DCdk6 complexes. Fbxo7 interacts directly with both Cdk6 and p27, and cooperatively increases cyclin D3 interactions with Cdk6 in vitro (Laman et al., 2005). In vivo, Fbxo7 overexpression in immortalised murine fibroblasts leads to their Cdk6-dependent transformation. These cells had increased levels of cyclin D-Cdk6 complexes and E2F activity, and formed tumours in athymic nude mice (Laman et al., 2005). Many mitogen and cytokine signalling pathways converge on cyclin D-Cdk activity, which -when overstimulated -promotes oncogenesis. Because of its Cdk6-dependent transforming activity, we propose that Fbxo7 functions as an oncogene.In U2OS and NIH3T3 cells, Fbxo7 has shown selectivity for Cdk6 over Cdk2 and Cdk4. Although the biochemical properties of Cdk4 and Cdk6 are similar, more-recent studies have indicated that differences can be discerned in their selective binding to cofactors (Sugimoto et al., 1999;Laman et al., 2005), preference for phosphorylation sites in pRb in vitro (Takaki et al., 2005), sensitivities to INK4 family members (Tourigny et al., 2002;Jones et al., 2007) and in vivo partnering with D-type cyclins (Ely et al., 2005). Also, in studies of knockout mice, tissue-specific defects are seen: Cdk4-knockout mice have impair...

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“…Indeed it has been reported that CDK6 blocks the myeloid differentiation by inhibiting the activity of AML-1. 45 In addition, CDK6 expression decreases during erythroid differentiation independently of the cell cycle. 31 Thus, if a similar down-regulation of CDK6 occurs during megakaryopoiesis, it will be associated with an increase in AML-1 activity leading both to a cell-cycle arrest and MK differentiation.…”

Section: Discussionmentioning

confidence: 99%

P19INK4D links endomitotic arrest and megakaryocyte maturation and is regulated by AML-1

Gilles

¹

,

Guièze

²

,

Bluteau

³

et al. 2008

Blood

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The molecular mechanisms that regulate megakaryocyte (MK) ploidization are poorly understood. Using MK differentiation from primary human CD34 ؉ cells, we observed that p19 INK4D expression was increased both at the mRNA and protein levels during ploidization. p19 INK4D knockdown led to a moderate increase (31.7% ؎ 5%) in the mean ploidy of MKs suggesting a role of p19 INK4D in the endomitotic arrest. This increase in ploidy was associated with a decrease in the more mature MK population (CD41 high CD42 high ) at day 9 of culture, which was related to a delay in differentiation. Inversely, p19 INK4D Until now, the best-studied model of polyploidization concerns megakaryocytes (MKs) in which after several replicative rounds, the process of classic mitosis is replaced by an endomitotic process. MK endomitosis is very similar to mitosis, but MKs skip anaphase B, telophase, and cytokinesis giving rise to a polyploid cell with a single polylobulated nucleus. 1,2 Although polyploidization is a part of the MK differentiation program, terminal differentiation that is associated with an increased platelet protein synthesis and the development of specific organelles requires an arrest of the cell cycle. Both the mitotic and endomitotic processes require an amplification of the DNA content. However, while mitosis leads to an increase in cell number, polyploidization results in an increase in the cell size and protein mass. In the case of MK, the platelet precursor, polyploidization increases platelet production.DNA replication is a regulated mechanism that depends on a well-organized network of the cyclin-dependent kinases (CDKs) and cyclin-dependent inhibitors (CDKIs) of the cell cycle. Progression through G1 to S phase of cell cycle in mammalian cells requires the activity of G1-cyclins (D and E) associated with their catalytic subunits (CDK4 and CDK6). The mitogen-stimulated cyclin D and CDK4/6 complexes phosphorylate the retinoblastoma protein (Rb) allowing its dissociation from E2Fs transcription factors. Activated E2Fs then regulate the expression of genes necessary for DNA synthesis during the S phase of cell cycle. Cells exit cell cycle and accumulate in a quiescent G 0 /G 1 state either in the absence of mitogenic stimuli when the cyclin D-dependent activity is lost or after CDK4/6 inhibition. CDKs are regulated by inhibitory phosphorylations mediated by the WEE1 and MYT1 kinases 3 or by induction of specific inhibitors from the INK4 and CIP/KIP families. Till now, 4 members of the INK4 family (p19 INK4D , p18 INK4C , p16 INK4A , and p15 INK4B ) are described to specifically block the activity of CDK4/6 either by forming inactive ternary INK4-CDK4/6-cyclin D or binary INK4-CDK4/6 complexes. 4 The members of the CIP/KIP family (p21 CIP1/WAF1 , p27 KIP1 , and p57 KIP2 ) inhibit cyclin A-or cyclin E-associated CDK2 activity, but stabilize cyclin D-associated CDK4/6 activity. 5,6 In MKs, a high level of 2 CIP/KIP family members, p21 CIP1 and p27 KIP1 ,7,8 and 1 member of the INK4 family, p16 INK4A , 7 was detected...

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Cdk6 blocks myeloid differentiation by interfering with Runx1 DNA binding and Runx1-C/EBPα interaction

Cited by 98 publications

References 29 publications

Knockdown of Fbxo7 reveals its regulatory role in proliferation and differentiation of haematopoietic precursor cells

Knockdown of Fbxo7 reveals its regulatory role in proliferation and differentiation of haematopoietic precursor cells

Knockdown of Fbxo7 reveals its regulatory role in proliferation and differentiation of haematopoietic precursor cells

P19INK4D links endomitotic arrest and megakaryocyte maturation and is regulated by AML-1

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