RESUMO
To maintain genome integrity and epigenetic information, mammalian cells must carefully coordinate the supply and deposition of histones during DNA replication. Here we report that the CUL4 E3 ubiquitin ligase complex CRL4(WDR23) directly regulates the stem-loop binding protein (SLBP), which orchestrates the life cycle of histone transcripts including their stability, maturation, and translation. Lack of CRL4(WDR23) activity is characterized by depletion of histones resulting in inhibited DNA replication and a severe slowdown of growth in human cells. Detailed analysis revealed that CRL4(WDR23) is required for efficient histone mRNA 3' end processing to produce mature histone mRNAs for translation. CRL4(WDR23) binds and ubiquitylates SLBP in vitro and in vivo, and this modification activates SLBP function in histone mRNA 3' end processing without affecting its protein levels. Together, these results establish a mechanism by which CUL4 regulates DNA replication and possible additional chromatin transactions by controlling the concerted expression of core histones.
Assuntos
Proteínas de Transporte/metabolismo , Replicação do DNA , DNA/biossíntese , Histonas/metabolismo , Proteínas Nucleares/metabolismo , Fase S , Ubiquitina-Proteína Ligases/metabolismo , Fatores de Poliadenilação e Clivagem de mRNA/metabolismo , Proteínas de Transporte/genética , Montagem e Desmontagem da Cromatina , DNA/genética , Regulação Neoplásica da Expressão Gênica , Células HEK293 , Células HeLa , Histonas/genética , Humanos , Proteínas Nucleares/genética , Ligação Proteica , Processamento de Terminações 3' de RNA , Interferência de RNA , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Fatores de Tempo , Transfecção , Complexos Ubiquitina-Proteína Ligase , Ubiquitina-Proteína Ligases/genética , Ubiquitinação , Fatores de Poliadenilação e Clivagem de mRNA/genéticaRESUMO
Histones are evolutionarily conserved proteins that together with DNA constitute eukaryotic chromatin in a defined stoichiometry. Core histones are dynamic scaffolding proteins that undergo a myriad of post-translational modifications, which selectively engage chromosome condensation, replication, transcription and DNA damage repair. Cullin4-RING ubiquitin E3 ligases are known to hold pivotal roles in a wide spectrum of chromatin biology ranging from chromatin remodeling and transcriptional repression, to sensing of cytotoxic DNA lesions. Our recent work uncovers an unexpected function of a CRL4 ligase upstream of these processes in promoting histone biogenesis. The CRL4WDR23 ligase directly controls the activity of the stem-loop binding protein (SLBP), which orchestrates elemental steps of canonical histone transcript metabolism. We demonstrate that non-proteolytic ubiquitination of SLBP ensures sufficient histone reservoirs during DNA replication and is vital for genome integrity and cellular fitness.