title: Cell cycle arrest by transforming growth factor beta1 near G1/S is mediated by acute abrogation of prereplication complex activation involving an Rb-MCM interaction.
abstract: Understanding inhibitory mechanisms of transforming growth factor beta1 (TGF-beta1) has provided insight into cell cycle regulation and how TGF-beta1 sensitivity is lost during tumorigenesis. We show here that TGF-beta1 utilizes a previously unknown mechanism targeting the function of prereplication complexes (pre-RCs) to acutely block S-phase entry when added to cells in late G(1), after most G(1) events have occurred. TGF-beta1 treatment in early G(1) suppresses Myc and CycE-Cdk2 and blocks pre-RC assembly. However, TGF-beta1 treatment in late G(1) acutely blocks S-phase entry by inhibiting activation of fully assembled pre-RCs, with arrest occurring prior to the helicase unwinding step at G(1)/S. This acute block by TGF-beta1 requires the function of Rb in late G(1) but does not involve Myc/CycE-Cdk2 suppression or transcriptional control. Instead, Rb mediates TGF-beta1 late-G(1) arrest by targeting the MCM helicase. Rb binds the MCM complex during late G(1) via a direct interaction with Mcm7, and TGF-beta1 blocks their dissociation at G(1)/S. Loss of Rb or overexpression of Mcm7 or its Rb-binding domain alone abrogates late-G(1) arrest by TGF-beta1. These results demonstrate that TGF-beta1 acutely blocks entry into S phase by inhibiting pre-RC activation and suggest a novel role for Rb in mediating this effect of TGF-beta1 through direct interaction with and control of the MCM helicase.
authors: Moffitt Cancer Center, Tampa, FL 33612, USA.
authors: Piyali
authors: P
authors: Mukherjee
authors: Sherry L
authors: SL
authors: Winter
authors: Mark G
authors: MG
authors: Alexandrow
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D019925:Cyclin A / Q000037:antagonists & inhibitors / Q000378:metabolism; D019927:Cyclin E / Q000037:antagonists & inhibitors / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016193:G1 Phase / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D051379:Mice; D064168:Minichromosome Maintenance Complex Component 7; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012319:RNA Polymerase II / Q000037:antagonists & inhibitors / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism*; D016196:S Phase / Q000187:drug effects* / Q000502:physiology; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*
chemical_list: D018797:Cell Cycle Proteins; D019925:Cyclin A; D019927:Cyclin E; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D016160:Retinoblastoma Protein; D053773:Transforming Growth Factor beta1; D004004:Dichlororibofuranosylbenzimidazole; C489403:Cdc7 protein, mouse; D017346:Protein Serine-Threonine Kinases; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D012319:RNA Polymerase II; C491086:Mcm7 protein, mouse; D064168:Minichromosome Maintenance Complex Component 7