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AMBRA1 regulates cyclin D to guard S-phase entry and genomic integrity.

Nature (2021-04-16)
Emiliano Maiani, Giacomo Milletti, Francesca Nazio, Søs Grønbæk Holdgaard, Jirina Bartkova, Salvatore Rizza, Valentina Cianfanelli, Mar Lorente, Daniele Simoneschi, Miriam Di Marco, Pasquale D'Acunzo, Luca Di Leo, Rikke Rasmussen, Costanza Montagna, Marilena Raciti, Cristiano De Stefanis, Estibaliz Gabicagogeascoa, Gergely Rona, Nélida Salvador, Emanuela Pupo, Joanna Maria Merchut-Maya, Colin J Daniel, Marianna Carinci, Valeriana Cesarini, Alfie O'sullivan, Yeon-Tae Jeong, Matteo Bordi, Francesco Russo, Silvia Campello, Angela Gallo, Giuseppe Filomeni, Letizia Lanzetti, Rosalie C Sears, Petra Hamerlik, Armando Bartolazzi, Robert E Hynds, David R Pearce, Charles Swanton, Michele Pagano, Guillermo Velasco, Elena Papaleo, Daniela De Zio, Apolinar Maya-Mendoza, Franco Locatelli, Jiri Bartek, Francesco Cecconi
ABSTRACT

Mammalian development, adult tissue homeostasis and the avoidance of severe diseases including cancer require a properly orchestrated cell cycle, as well as error-free genome maintenance. The key cell-fate decision to replicate the genome is controlled by two major signalling pathways that act in parallel-the MYC pathway and the cyclin D-cyclin-dependent kinase (CDK)-retinoblastoma protein (RB) pathway1,2. Both MYC and the cyclin D-CDK-RB axis are commonly deregulated in cancer, and this is associated with increased genomic instability. The autophagic tumour-suppressor protein AMBRA1 has been linked to the control of cell proliferation, but the underlying molecular mechanisms remain poorly understood. Here we show that AMBRA1 is an upstream master regulator of the transition from G1 to S phase and thereby prevents replication stress. Using a combination of cell and molecular approaches and in vivo models, we reveal that AMBRA1 regulates the abundance of D-type cyclins by mediating their degradation. Furthermore, by controlling the transition from G1 to S phase, AMBRA1 helps to maintain genomic integrity during DNA replication, which counteracts developmental abnormalities and tumour growth. Finally, we identify the CHK1 kinase as a potential therapeutic target in AMBRA1-deficient tumours. These results advance our understanding of the control of replication-phase entry and genomic integrity, and identify the AMBRA1-cyclin D pathway as a crucial cell-cycle-regulatory mechanism that is deeply interconnected with genomic stability in embryonic development and tumorigenesis.

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