Ribosome biogenesis is an energy consuming process which takes place mainly in the nucleolus. By producing ribosomes to fuel protein synthesis, it is tightly connected with cell growth and cell cycle control. Perturbation of ribosome biogenesis leads to the activation of p53 tumor suppressor protein promoting processes like cell cycle arrest, apoptosis or senescence. This ribosome biogenesis stress pathway activates p53 through sequestration of MDM2 by a subset of ribosomal proteins (RPs), thereby stabilizing p53. Here, we identify human HEATR1, as a nucleolar protein which positively regulates ribosomal RNA (rRNA) synthesis. Downregulation of HEATR1 resulted in cell cycle arrest in a manner dependent on p53. Moreover, depletion of HEATR1 also caused disruption of nucleolar structure and activated the ribosomal biogenesis stress pathway - RPL5 / RPL11 dependent stabilization and activation of p53. These findings reveal an important role for HEATR1 in ribosome biogenesis and further support the concept that perturbation of ribosome biosynthesis results in p53-dependent cell cycle checkpoint activation, with implications for human pathologies including cancer.

• Klíčová slova
• HEATR1, cancer, p53, ribosome biogenesis, ribosome biogenesis stress,
• MeSH
• biogeneze organel * MeSH
• fyziologický stres MeSH
• genetická transkripce * MeSH
• jaderné proteiny metabolismus   MeSH
• kontrolní body buněčného cyklu MeSH
• lidé MeSH
• nádorové buněčné linie MeSH
• nádorový supresorový protein p53 metabolismus   MeSH
• proliferace buněk MeSH
• proteiny vázající RNA metabolismus   MeSH
• protoonkogenní proteiny c-mdm2 metabolismus   MeSH
• ribozomální proteiny metabolismus   MeSH
• ribozomy metabolismus   MeSH
• RNA ribozomální biosyntéza   MeSH
• RNA-polymerasa I genetika   MeSH
• signální transdukce MeSH
• vedlejší histokompatibilní antigeny metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• HEATR1 protein, human MeSH Prohlížeč
• jaderné proteiny MeSH
• MDM2 protein, human MeSH Prohlížeč
• nádorový supresorový protein p53 MeSH
• proteiny vázající RNA MeSH
• protoonkogenní proteiny c-mdm2 MeSH
• ribozomální proteiny MeSH
• RNA ribozomální MeSH
• RNA-polymerasa I MeSH
• vedlejší histokompatibilní antigeny MeSH

Based on a series of basic, preclinical and clinical studies, the Poly (ADP-ribose) Polymerase 1 (PARP1) inhibitor, olaparib, has recently been approved for use in ovarian cancer patients with BRCA1 or BRCA2 mutations. By identifying novel predictive biomarkers of tumour cell sensitivity to olaparib, it is possible that the utility of PARP inhibitors could be extended beyond this patient subgroup. Many of the known genetic determinants of PARP inhibitor response have key roles in DNA damage response (DDR) pathways. Although protein ubiquitylation is known to play an important role in regulating the DDR, the exact mechanisms by which this occurs are not fully understood. Using two parallel RNA interference-based screening approaches, we identified the E3 ubiquitin ligase, CBLC, as a candidate biomarker of response to olaparib. We validated this observation by demonstrating that silencing of CBLC causes increased sensitivity to olaparib in breast cancer cell line models and that defective homologous recombination (HR) DNA repair is the likely cause. This data provides an example of how defects in the ubiquitin machinery have the potential to influence the response of tumour cells to PARP inhibitors.

• Klíčová slova
• CBLC, DNA damage response, PARP inhibitors, RNA interference screens, ubiquitin-proteasome system,
• MeSH
• časové faktory MeSH
• ftalaziny farmakologie   MeSH
• lidé MeSH
• nádorové buněčné linie MeSH
• nádory prsu farmakoterapie   enzymologie   genetika   patologie   MeSH
• oprava DNA MeSH
• PARP inhibitory farmakologie   MeSH
• piperaziny farmakologie   MeSH
• poly(ADP-ribosa)polymerasa 1 MeSH
• poly(ADP-ribosa)polymerasy genetika   metabolismus   MeSH
• posttranslační úpravy proteinů MeSH
• protein BRCA2 genetika   metabolismus   MeSH
• protoonkogenní proteiny c-cbl genetika   metabolismus   MeSH
• regulace genové exprese u nádorů MeSH
• rekombinace genetická MeSH
• RNA interference MeSH
• signální transdukce účinky léků   MeSH
• transfekce MeSH
• ubikvitinace MeSH
• viabilita buněk účinky léků   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• Check Tag
• lidé MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• BRCA2 protein, human MeSH Prohlížeč
• CBLC protein, human MeSH Prohlížeč
• ftalaziny MeSH
• olaparib MeSH Prohlížeč
• PARP inhibitory MeSH
• PARP1 protein, human MeSH Prohlížeč
• piperaziny MeSH
• poly(ADP-ribosa)polymerasa 1 MeSH
• poly(ADP-ribosa)polymerasy MeSH
• protein BRCA2 MeSH
• protoonkogenní proteiny c-cbl MeSH

The DNA damage response factor 53BP1 functions at the intersection of two major double strand break (DSB) repair pathways--promoting nonhomologous end-joining (NHEJ) and inhibiting homology-directed repair (HDR)--and integrates cellular inputs to ensure their timely execution in the proper cellular contexts. Recent work has revealed that 53BP1 controls 5' end resection at DNA ends, mediates synapsis of DNA ends, promotes the mobility of damaged chromatin, improves DSB repair in heterochromatic regions, and contributes to lethal mis-repair of DSBs in BRCA1-deficient cells. Here we review these aspects of 53BP1 and discuss new data revealing how 53BP1 is loaded onto chromatin and uses its interacting factors Rif1 and PTIP to promote NHEJ and inhibit HDR.

• Klíčová slova
• 53BP1, BRCA1, CSR, HDR, NHEJ, PARPi, PTIP, Rif1, V(D)J, resection, telomere,
• MeSH
• 53BP1 MeSH
• intracelulární signální peptidy a proteiny metabolismus   MeSH
• lidé MeSH
• oprava DNA * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• 53BP1 MeSH
• intracelulární signální peptidy a proteiny MeSH
• TP53BP1 protein, human MeSH Prohlížeč

Cells are constantly challenged by DNA damage and protect their genome integrity by activation of an evolutionary conserved DNA damage response pathway (DDR). A central core of DDR is composed of a spatiotemporally ordered net of post-translational modifications, among which protein phosphorylation plays a major role. Activation of checkpoint kinases ATM/ATR and Chk1/2 leads to a temporal arrest in cell cycle progression (checkpoint) and allows time for DNA repair. Following DNA repair, cells re-enter the cell cycle by checkpoint recovery. Wip1 phosphatase (also called PPM1D) dephosphorylates multiple proteins involved in DDR and is essential for timely termination of the DDR. Here we have investigated how Wip1 is regulated in the context of the cell cycle. We found that Wip1 activity is downregulated by several mechanisms during mitosis. Wip1 protein abundance increases from G(1) phase to G(2) and declines in mitosis. Decreased abundance of Wip1 during mitosis is caused by proteasomal degradation. In addition, Wip1 is phosphorylated at multiple residues during mitosis, and this leads to inhibition of its enzymatic activity. Importantly, ectopic expression of Wip1 reduced γH2AX staining in mitotic cells and decreased the number of 53BP1 nuclear bodies in G(1) cells. We propose that the combined decrease and inhibition of Wip1 in mitosis decreases the threshold necessary for DDR activation and enables cells to react adequately even to modest levels of DNA damage encountered during unperturbed mitotic progression.

• Klíčová slova
• DNA damage response, Wip1 phosphatase, cell cycle, mitotic progression, γH2AX,
• MeSH
• DNA primery genetika   MeSH
• fluorescenční protilátková technika MeSH
• fosforylace MeSH
• hmotnostní spektrometrie MeSH
• kontrolní body M fáze buněčného cyklu fyziologie   MeSH
• kvantitativní polymerázová řetězová reakce MeSH
• lidé MeSH
• malá interferující RNA genetika   MeSH
• mitóza fyziologie   MeSH
• nádorové buněčné linie MeSH
• poškození DNA * MeSH
• proteinfosfatasa 2C MeSH
• proteinfosfatasy metabolismus   MeSH
• regulace genové exprese fyziologie   MeSH
• signální transdukce fyziologie   MeSH
• transfekce MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA primery MeSH
• malá interferující RNA MeSH
• PPM1D protein, human MeSH Prohlížeč
• proteinfosfatasa 2C MeSH
• proteinfosfatasy MeSH