Survey
NF-κB and cell-cycle regulation: the cyclin connection

https://doi.org/10.1016/S1359-6101(00)00018-6Get rights and content

Abstract

The cyclins are a family of proteins that are centrally involved in cell cycle regulation and which are structurally identified by conserved “cyclin box” regions. They are regulatory subunits of holoenzyme cyclin-dependent kinase (CDK) complexes controlling progression through cell cycle checkpoints by phosphorylating and inactivating target substrates. CDK activity is controlled by cyclin abundance and subcellular location and by the activity of two families of inhibitors, the cyclin-dependent kinase inhibitors (CKI). Many hormones and growth factors influence cell growth through signal transduction pathways that modify the activity of the cyclins. Dysregulated cyclin activity in transformed cells contributes to accelerated cell cycle progression and may arise because of dysregulated activity in pathways that control the abundance of a cyclin or because of loss-of-function mutations in inhibitory proteins.

Analysis of transformed cells and cells undergoing mitogen-stimulated growth implicate proteins of the NF-κB family in cell cycle regulation, through actions on the CDK/CKI system. The mammalian members of this family are Rel-A (p65), NF-κB1 (p50; p105), NF-κB2 (p52; p100), c-Rel and Rel-B. These proteins are structurally identified by an amino-terminal region of about 300 amino acids, known as the Rel-homology domain. They exist in cytoplasmic complexes with inhibitory proteins of the IκB family, and translocate to the nucleus to act as transcription factors when activated. NF-κB pathway activation occurs during transformation induced by a number of classical oncogenes, including Bcr/Abl, Ras and Rac, and is necessary for full transforming potential. The avian viral oncogene, v-Rel is an NF-κB protein. The best explored link between NF-κB activation and cell cycle progression involves cyclin D1, a cyclin which is expressed relatively early in the cell cycle and which is crucial to commitment to DNA synthesis. This review examines the interactions between NF-κB signaling and the CDK/CKI system in cell cycle progression in normal and transformed cells. The growth-promoting actions of NF-κB factors are accompanied, in some instances, by inhibition of cellular differentiation and by inhibition of programmed cell death, which involve related response pathways and which contribute to the overall increase in mass of undifferentiated tissue.

Section snippets

The NF-κB protein family

The NF-κB/Rel family of transcription factors are active in inflammatory and immune cell response, cell cycle regulation, differentiation and protection from apoptosis (reviewed in refs. [1] and [2]. The mammalian members of the NF-κB/Rel family are Rel-A (p65), Rel-B, c-Rel, NF-κB1 (p50/p105) and NF-κB2 (p52/p100) [3], [4], [5], [6], [7], [8]. They all have an extended amino-terminal region knows as the Rel homology domain (RHD), which incorporates a leucine zipper dimerization domain, a

Cyclins, cyclin-dependent kinases and cyclin-dependent kinase inhibitors in cell growth regulation

The cyclin-dependent kinases (CDK's) are important regulators of the mammalian cell cycle (for reviews see [91]). CDK activity is modulated by mitogens and growth factors, by pathways that include NF-κB factors. Escape of CDK's from normal regulation, or escape of downstream events from CDK control, frequently accompanies cellular transformation. The activities of CDK4, CDK6, CDK2 and the Cdc2 kinase are expressed differentially during the cell cycle, in response to changes in the abundance of

Cyclin-dependent kinase inhibitors

CDK complexes are subject to regulation by proteins of two families. The Ink4 proteins act to dissociate cyclin D1/CDK4/CDK6 complexes [127], [128], [129], whilst the p2l family proteins inhibit CD1K activity in some circumstances [130], [131]. The Ink4 family includes p16Ink4a, p15Ink4b, p18Ink4c and p19Ink4d. Additionally, the p16Ink4a gene locus also encodes a further protein, p19ARF (pl4ARF in human cells) [132] in an alternate reading frame, which shares CD1K inhibitory activity. In the

Cyclin-dependent kinase function

The CDK's themselves regulate cell-cycle controlling genes and proteins through kinase functions and through direct protein-protein interactions (reviewed in ref. [91]). Prominent amongst these are interactions with transcription factors. For example, cyclin A/CDK2 and cyclin B/Cdc2 phosphorylate p53, enhancing transactivation through the p53 response element [152]. Cyclin A/CDK2 phosphorylation of B-myb enhances transcriptional activity through the MBS site [153]. Conversely, Cyclin A/CDK2

NF-κB in mitogen-stimulated cell growth

Variations in NF-κB activity through the cell cycle, enhanced activity after mitogenic stimulation, the v-Rel oncogene and apoptosis of Rel-A-deficient cells together drew attention to a role for NFκB factors in cell growth and survival. The association between normal growth and NF-κB activation has been noted in many cells and tissues. Enhanced NF-κB is apparent during the G0/G1 transition in fibroblasts [164] and is induced by mitogenic stimuli, including serum, in G0 arrested 3T3 fibroblasts

NF-κB and growth of transformed cells

Disordered expression of NF-κB family proteins in mammalian and avian neoplasia has drawn attention to roles in transformation, both through abnormal NF-κB proteins and though oncogenic protein activation of NF-κB signaling pathways. V-Rel was initially identified in transformed avian hemopoietic cells and is an oncogenic NF-κB family member which is encoded by the Rev-T avian retrovirus (for review see ref. [198]). Abnormal NF-κB family proteins also occur in a small percentage of human B and

Oncogene activation of NF-κB

Activation of NF-κB occurs in cells transformed by several classical oncoproteins including transforming Ras and Rac, the chimeric Bcr-Abl oncoproteins and transforming viral proteins. NF-κB is required for focus formation by NIH 3T3 cells expressing transforming Ras [68]. The observations that Ras activated cyclin D1 [107], and that this was required for Ras-induced transformation [205], [206] suggested that cyclin D1 itself may be a target of NF-κB activity. Similarly, transforming mutants of

NF-κB increases cyclin D1 expression

Observations on transformed cells and cells undergoing normal mitogen-stimulated growth, implicate proteins of the NF-κB family in cell cycle regulation, through actions on the CDK/CKI system. Experiments in many cell types now indicate that NF-κB acts through increasing the abundance of cyclin D1 and thus the activity of the cyclin D1 kinase holoenzyme complex. The role of NF-κB factors in controlling the cell cycle and cyclin D1 has been well shown in investigations that used the IκB “super

NF-κB, cyclin D1 and cell differentiation

Terminal differentiation of mammalian cells is generally accompanied by cessation of growth. In vitro myogenic differentiation models have demonstrated that NF-κB has roles in both cell cycling and suppression of terminal differentiation. Enhanced expression of cyclin D1 is central to both roles. Like other cell types, C2C12 myoblasts express the NF-κB1/Rel-A heterodimer whilst proliferating, and proliferate more slowly if NF-κB is inhibited [104]. Inducing myogenic differentiation, however,

NF-κB signaling in oncogene-transformed cells

It is therefore established that NF-κB factors enhance cell cycle progression in widely different cells types after exposure to mitogenic stimuli, through activating cyclin D1 transcription. Activation of NF-κB also occurs in cells transformed by several classical oncoproteins, including transforming Ras and Rac, the chimeric Bcr-Abl oncoproteins and transforming viral proteins, [68], [107], [205], [206], [207], [208], [209]. The observations have prompted examination of NF-κB-cyclin D1 pathway

Other NF-κB interactions with the cyclin/CDK/CKI system

There is also some evidence that the cyclin A promoter may be transcriptionally activated by NF-κB, although it has no consensus NF-κB sites [69]. Consistent with this, IκB-SR suppressed cyclin A abundance when expressed in myoblastic cell [104]. IκB-SR does not affect CDK2 abundance, but the rise in CDK2 activity which normally accompanies release from G0 is delayed in fibroblasts expressing IκB-SR [103]. This may be related to reduced cyclin A abundance. Interestingly, though, the cyclin

Conclusion

Increased NF-κB activity during growth of mitogen-stimulated and transformed cells has therefore been linked to cell cycle progression through transcriptional activation of the cyclin D1 gene, leading to increased abundance of cyclin D1 and increased activity of cyclin D1 kinase. Although this pathway has been observed in multiple cell types and under different conditions, it is unlikely to be the only link between NF-κB factor activity and cell cycle progression. Future research will tell us

Acknowledgements

We are grateful to Drs. M. Horwitz, and J. Friedman for helpful discussions. This work was supported in part by RO1CA70897, RO1CA75503, 5-P30-CA13330-26 (R.G.P.).

References (222)

  • S. Hoshi et al.

    Regulation of vascular smooth muscle cell proliferation by nuclear factor-kappaB and its inhibitor, I-kappaB

    J. Biol. Chem.

    (2000)
  • S. Heck et al.

    Insulin-like growth factor-1-mediated neuroprotection against oxidative stress is associated with activation of nuclear factor kappaB

    J. Biol. Chem.

    (1999)
  • M. Karin

    The beginning of the end: IkappaB kinase (IKK) and NF-kappaB activation

    J. Biol. Chem.

    (1999)
  • C.H. Regnier et al.

    Identification and characterization of an IkappaB kinase

    Cell

    (1997)
  • E. Zandi et al.

    The IkappaB kinase complex (IKK) contains two kinase subunits, IKKalpha and IKKbeta, necessary for IkappaB phosphorylation and NF-kappaB activation

    Cell

    (1997)
  • T.S. Finco et al.

    Mechanistic aspects of NF-kappa B regulation: the emerging role of phosphorylation and proteolysis

    Immunity

    (1995)
  • J.E. Thompson et al.

    I kappa B-beta regulates the persistent response in a biphasic activation of NF-kappa B

    Cell

    (1995)
  • T. Huxford et al.

    The crystal structure of the IkappaBalpha/NF-kappaB complex reveals mechanisms of NF-kappaB inactivation

    Cell

    (1998)
  • M.D. Jacobs et al.

    Structure of an IkappaBalpha/NF-kappaB complex

    Cell

    (1998)
  • J. Ye et al.

    Regulation of the NF-kappaB activation pathway by isolated domains of FIP3/IKKgamma, a component of the IkappaB-alpha kinase complex

    J. Biol. Chem.

    (2000)
  • S.Q. Zhang et al.

    Recruitment of the IK signalosome to the p55 TNF receptor:RIP and A20 bind to NEMO (IKK_) upon receptor stimulation

    Immunity

    (2000)
  • M. Karin et al.

    The IκB kinase (IKK) and NF-κB: key elements of proinflammatory signalling

    Sem. Immunol.

    (2000)
  • R.T. Peters et al.

    IKKε is part of a novel PMA-inducible IκB kinase complex

    Mol. Cell.

    (2000)
  • M.-J. Yin et al.

    HTLV-I Tax protein binds to MEKK1 to stimulate IκB kinase activity and NF-κB activation

    Cell

    (1998)
  • F.S. Lee et al.

    Activation of the IκB kinase complex by MEKK1, a kinase of the JNK pathway

    Cell

    (1997)
  • Q. Zhao et al.

    Mitogen-activated protein kinase/ERK kinase kinases 2 and 3 activate nuclear factor-kappaB through IkappaB kinase-alpha and IkappaB kinase-beta

    J. Biol. Chem.

    (1999)
  • X. Lin et al.

    The proto-oncogene Cot kinase participates in CD3/CD28 induction of NF-kappaB acting through the NF-kappaB-inducing kinase and IkappaB kinases

    Immunity

    (1999)
  • E.W. Harhaj et al.

    IKKgamma serves as a docking subunit of the IkappaB kinase (IKK) and mediates interaction of IKK with the human T-cell leukemia virus Tax protein

    J. Biol. Chem.

    (1999)
  • D.Y. Jin et al.

    Role of adapter function in oncoprotein-mediated activation of NF-kappaB. Human T-cell leukemia virus type I Tax interacts directly with IkappaB kinase gamma

    J. Biol. Chem.

    (1999)
  • T.S. Finco et al.

    Oncogenic Ha-Ras-induced signaling activates NF-κB transcriptional activity, which is required for cellular transformation

    J. Biol. Chem.

    (1997)
  • D. Joyce et al.

    Integration of Rac-dependent regulation of cyclin D1 transcription through an NF-κB-dependent pathway

    J. Biol. Chem.

    (1999)
  • S. Montaner et al.

    Multiple signalling pathways lead to the activation of the nuclear factor kappaB by the Rho family of GTPases

    J. Biol. Chem.

    (1998)
  • T. Machleidt et al.

    Sphingomyelinase activates proteolytic I kappa B-alpha degradation in a cell-free system

    J. Biol. Chem.

    (1994)
  • P. Brennan et al.

    Effects of oxidants and antioxidants on nuclear factor kappa B activation in three different cell lines: evidence against a universal hypothesis involving oxygen radicals

    Biochim. Biophys. Acta.

    (1995)
  • K. Schulze-Osthoff et al.

    Redox signalling by transcription factors NF-kappa B and AP-1 in lymphocytes

    Biochem. Pharmacol.

    (1995)
  • P. Tan et al.

    Recruitment of a ROC1-CUL1 ubiquitin ligase by Skp1 and HOS to catalyze the ubiquitination of IκBα

    Cell

    (1999)
  • Z.J. Chen et al.

    Site-specific phosphorylation of IκBα by a novel ubiquitination-dependent protein kinase activity

    Cell

    (1996)
  • R.A. Weinberg

    The retinoblastoma protein and cell cycle control

    Cell

    (1995)
  • T. Motokura et al.

    Cyclin D and oncogenesis

    Curr. Opin. Genet. Dev.

    (1993)
  • S. Ghosh et al.

    NF-kappa B and Rel proteins: evolutionarily conserved mediators of immune responses

    Annu. Rev. Immunol.

    (1998)
  • V. Bours et al.

    A novel mitogen-inducible gene product related to p50/p105-NF-kappa B participates in transactivation through a kappa B site

    Mol. Cell. Biol.

    (1992)
  • S.M. Ruben et al.

    Isolation of a rel-related human cDNA that potentially encodes the 65-κD subunit of NF-kappa B

    Science

    (1991)
  • R.M. Schmid et al.

    Cloning of an NF-kappa B subunit which stimulates HIV transcription in synergy with p65

    Nature

    (1991)
  • F.E. Chen et al.

    Crystal structure of p50/p65 heterodimer of transcription factor NF-kappaB bound to DNA

    Nature

    (1998)
  • I.M. Verma et al.

    Rel/NF-kappa B/I kappa B family: intimate tales of association and dissociation

    Genes. and. Development. 5

    (1995)
  • P. Dobrzanski et al.

    Differential interactions of Rel-NF-kappa B complexes with I kappa B alpha determine pools of constitutive and inducible NF-kappa B activity

    EMBO J.

    (1994)
  • M. Neumann et al.

    RelA/p65 is a molecular target for the immunosuppressive action of protein kinase A

    EMBO J.

    (1995)
  • K.A. Sheppard et al.

    Transcriptional activation by NF-kappaB requires multiple coactivators

    Mol. Cell. Biol.

    (1999)
  • A.A. Beg et al.

    I kappa B interacts with the nuclear localization sequences of the subunits of NF-kappa B: a mechanism for cytoplasmic retention

    Genes. and. Develop.

    (1992)
  • H.C. Liou et al.

    The NF-kappa B p50 precursor, p105, contains an internal I kappa B-like inhibitor that preferentially inhibits p50

    EMBO J.

    (1992)
  • Cited by (354)

    View all citing articles on Scopus
    View full text