The Biology of Cancer Chapter 8: pRb and Control of the Robert A. Weinberg The Biology of Cancer First Edition Chapter 8: pRb and Control of the Cell Cycle Clock Copyright © Garland Science 2007

Cell cycle clock is the master governor to decide proliferation or not Figure 8.1 The Biology of Cancer (© Garland Science 2007)

Chromosomal instability (genomic instability) is one of hallmark of cancers Figure 8.5a The Biology of Cancer (© Garland Science 2007)

Cells make decision about growth and quiescence during a specific period in the G1 stage Figure 8.6 The Biology of Cancer (© Garland Science 2007)

The Cell cycle system, three major euk systems; in yeast, frog, mammalian cells Yeast; Fission ( S. pombe) and budding yeast ( S. cerevisiae) - genetically useful; genetic manipulation Haploid state Cdc genes; cell-division cycle genes; ts mutant (permissive or restrictive condition *No nuclear envelop breakage during mitosis * budding yeast; no clear G2 phase

Isolation of wild-type cell-division cycle (CDC) genes from S Isolation of wild-type cell-division cycle (CDC) genes from S. cerevisiae carrying temperature-sensitive mutations in these genes Figure 13-4

Two classes of mutations in S Two classes of mutations in S. pombe produce either elongated or very small cells S. pombe Cdc2-Cdc13 heterodimer is equivalent to Xenopus MPF (Cdc2 is cdk, Cdc13 is cyclin B) Figure 13-11

MPF promotes maturation of Xenopus laevis oocytes Figure 13-5

MPF promotes mitosis in somatic cells Figure 13-6

Cell cycle-dependent fluctuations in the cyclin B levels Cyclin B levels and MPF activity change together in cycling Xenopus egg extracts, MPF is a dimer of a mitotic cyclin and cyclin-dependent kinase (cdk) Figure 8.9 The Biology of Cancer (© Garland Science 2007)

Ossilation of cyclin levels during the cell cycle Figure 8.10 The Biology of Cancer (© Garland Science 2007)

Cyclins and Cdk constitute the core components of the cell cycle clock Figure 8.7 The Biology of Cancer (© Garland Science 2007)

Components of the cell cycle control system *The control of cell cycle regulation; a clock or timer; specific time -correct order-once per cycle -binary switch on/off system -adaptability; specific cell types or environmental Checkpoint control; delay the cell cycle progression or arrest the cell cycle in response to signals -send a negative signal rather than removal of positive signal -provide time for DNA repair or prevent the disaster

-Cyclin-dependent kinase (Cdks) The cell cycle regulation are based on cyclically activated protein kinase; Multiple cdks and cyclins regulate passage of mammalian cells through the cell cycle -Cyclin-dependent kinase (Cdks) -cdk regulators; *different cyclins, *level of cyclins (transcriptionally or proteolysis), * inhibitors (p21, 27, p16, p57 etc) * phosphorylation or dephosphorylation (Cdc25, kinase)

Cdk activity are regulated by inhibitory phosphorylation and by CIPs

The cell cycle control system depends cyclical proteolysis; SCF, APC

Mitogenic signaling increase the level of cylin D Figure 8.11b The Biology of Cancer (© Garland Science 2007)

Control of cyclin levels during the cell cycle and Cdk are also regulated by CdkIs Figure 8.12 The Biology of Cancer (© Garland Science 2007)

Control of cell cycle progression by various mitogenic signals Inhibitory signal TGF-beta induce the p15 CDKI Stimulatory signal Figure 8.14a The Biology of Cancer (© Garland Science 2007)

Suppression of p27 function by Akt/PKB in human breast cancer Nuclear P27 Figure 8.16a The Biology of Cancer (© Garland Science 2007)

Interaction of CDK Is with Cylin-Cdks; P27,p21 differentially affect the Cdks activity p21, p27 stimulate Cdk4/6 at early G1, but inhibit Cdk2 from late G1-to M

The level of p27 is elevated in the post-mitotic cells or differentiated cells Brdu p27 Non-dividing granule cells of the cerebellum Figure 8.18a The Biology of Cancer (© Garland Science 2007)

Cell cycle phosphorylation of Rb; Rb is the determinant of R point (Active Rb) (Inactive Rb) Figure 8.19 The Biology of Cancer (© Garland Science 2007)

Rb bind to and inhibit E2F TFs Figure 8.23a The Biology of Cancer (© Garland Science 2007)

E2F TFs function as activator or repressor Figure 8.23d The Biology of Cancer (© Garland Science 2007)

Structure of Rb and E2F Figure 8.23b The Biology of Cancer (© Garland Science 2007)

Modification of chromatin by Rb Figure 8.24a The Biology of Cancer (© Garland Science 2007)

Positive feedback loops and the irreversible of cell cycle progression Cdk2 Rb E2F E-Cdk2 p27 Figure 8.25a The Biology of Cancer (© Garland Science 2007)

Counterbalancing the level of Cyclin D by several mitogenic signaling G1-S progression Figure 8.26 The Biology of Cancer (© Garland Science 2007)

Myc : bHLH TF, contributes to the cell differentiation and cell cycle progression Figure 8.27 The Biology of Cancer (© Garland Science 2007)

Oncogenic activity of Myc overexpression Many Myc-binding sites of targets Figure 8.29 The Biology of Cancer (© Garland Science 2007)

Table 8.2 The Biology of Cancer (© Garland Science 2007)

How TGF-beta blocks the cell cycle progression Figure 8.31 The Biology of Cancer (© Garland Science 2007)

Viral oncoprotein inhibit the Rb by direct binding; E1A, T-Ag are sequestering and inactivating Rb E7 tags Rb for its ubiquitination and destruction Figure 8.20 The Biology of Cancer (© Garland Science 2007)

Rb also control the differentiation Myoblasts only differentiate after proliferation stops. When growth factors are present, MyoD & Myf-5 are expressed and the myoblasts proliferate & do not differentiate. Removal of growth factors causes myoblasts to withdraw from the cell cycle; fusion and differentiation follow. The retinoblastoma protein (Rb) can block cell growth and is inactivated by phosphorylation in proliferating cells. Dephosphorylation of Rb & blockage of cell cycle is a "differentiation decision". Cdk phosphorylate MyoD and promotes its destruction Id binds to and sequest Rb and promote cell cycle progression, If Id is overexoressed ? What happen?

Table 8.3 The Biology of Cancer (© Garland Science 2007)

Table 8.4 The Biology of Cancer (© Garland Science 2007)

Figure 8.35 The Biology of Cancer (© Garland Science 2007)

Amplification of cyclin D in cancer cells Figure 8.36 The Biology of Cancer (© Garland Science 2007)

Suppression of p27,free Cyclin E, Rb by Skp2 Figure 8.37a The Biology of Cancer (© Garland Science 2007)

Figure 8.37d The Biology of Cancer (© Garland Science 2007)

Figure 8.38 The Biology of Cancer (© Garland Science 2007)