Project description:RNA was extracted from three independent wild type cell populations treated for 7 days with Hydroxyurea and allowed to recover for another seven days, as well as from three untreated parallel controls. Extraction was performed using Trizol. Microarray hybridisations were performed using total RNA and the Affymetrix Chicken Genome array. FANCJ and WRN/BLM mutants have been performed at the same day as the WT \PS_2010\ and HU treated cells at the same day as WT \08_2012\
Project description:Hydroxyurea (HU) is toxic to Sulfolobus cells. To address the basis of the HU toxicity, we performed transcriptome analyses on untreated cells and cells following exposure to 5 mM HU for 4 hours.
Project description:BLM protein has been shown to play an important role in homologous recombination (HR) repair. We report that BLM interacts with RAD54 (another HR repair protein) to enhance its chromatin remodeling function. This experiment identifies that BLM gets recruited to different genetic loci even in the absence of damage, possibly along with RAD54 chromatin remodeler.
Project description:The Bloom syndrome DNA helicase BLM contributes to chromosome stability through its roles in double-strand break repair by homologous recombination and DNA replication fork restart during the replication stress response. Loss of BLM activity leads to Bloom syndrome, which is characterized by extraordinary cancer risk and small stature. Here, we have analyzed the composition of the BLM complex in unperturbed cells and identified a direct physical interaction with the Mcm6 subunit of the minichromosome maintenance (MCM) complex by co-immunopecipitations using endogenous and recombinant proteins as well as two-hybrid analysis.
Project description:Basal cell carcinomas (BCCs) have relative genomic stability and relatively benign clinical behavior but whether these two are related causally is unknown. To investigate the effects of introducing genomic instability into murine BCCs, we have compared ionizing radiation-induced tumorigenesis in Ptch1+/- mice vs. that in Ptch1+/- mice carrying mutant Blm alleles. We found that BCCs in Ptch1+/- Blmtm3Brd/tm3Brd mice had a trend towards greater genomic instability as measured by array CGH and that these mice developed significantly more microscopic BCCs than did Ptch1+/- Blm+/tm3Brd or Ptch1+/- Blm+/+ mice. The mutant Blm alleles also markedly enhanced the formation of rhabdomyosarcomas (RMS), another cancer to which Ptch1+/- mice and PTCH1+/- (basal cell nevus syndrome) patients are susceptible. Highly recurrent but different copy number changes were associated with the two tumor types and included losses of chromosomes 4 and 10 in all BCCs and gain of chromosome 10 in 80% of RMSs. Loss of chromosome 11 and 13, including the Trp53 and Ptch1 loci respectively, occurred frequently in BCCs, suggesting tissue-specific selection for genes or pathways that collaborate with Ptch deficiency in tumorigenesis. Despite the quantitative differences, there was no dramatic qualitative difference in the BCC or RMS tumors associated with the mutant Blm genotype. We investigated the effect of Blm deficiency on ionizing radiation-induced basal cell carcinoma and rhabdomyosarcoma tumorigenesis in Ptch1+/- mice. Six BCC and five RMS samples were obtained from separate mice. Liver tissue from each mouse was used as the normal reference.
Project description:Basal cell carcinomas (BCCs) have relative genomic stability and relatively benign clinical behavior but whether these two are related causally is unknown. To investigate the effects of introducing genomic instability into murine BCCs, we have compared ionizing radiation-induced tumorigenesis in Ptch1+/- mice vs. that in Ptch1+/- mice carrying mutant Blm alleles. We found that BCCs in Ptch1+/- Blmtm3Brd/tm3Brd mice had a trend towards greater genomic instability as measured by array CGH and that these mice developed significantly more microscopic BCCs than did Ptch1+/- Blm+/tm3Brd or Ptch1+/- Blm+/+ mice. The mutant Blm alleles also markedly enhanced the formation of rhabdomyosarcomas (RMS), another cancer to which Ptch1+/- mice and PTCH1+/- (basal cell nevus syndrome) patients are susceptible. Highly recurrent but different copy number changes were associated with the two tumor types and included losses of chromosomes 4 and 10 in all BCCs and gain of chromosome 10 in 80% of RMSs. Loss of chromosome 11 and 13, including the Trp53 and Ptch1 loci respectively, occurred frequently in BCCs, suggesting tissue-specific selection for genes or pathways that collaborate with Ptch deficiency in tumorigenesis. Despite the quantitative differences, there was no dramatic qualitative difference in the BCC or RMS tumors associated with the mutant Blm genotype.
Project description:Transcriptionally active loci are particularly prone to breakage and mounting evidence suggest that DNA Double-Strand Breaks arising in active genes are handled by a dedicated repair pathway, Transcription-Coupled DSB Repair (TC-DSBR), that entails R-loop accumulation and dissolution. Here, we uncovered a function for the Bloom RecQ DNA helicase (BLM) in TC-DSBR in human cells. BLM is recruited in a transcription dependent-manner at DSBs where it fosters resection, RAD51 binding and accurate Homologous Recombination repair. However, in an R-loop dissolution-deficient background, we found that BLM promotes cell death. We report that upon excessive R-loop accumulation, DNA synthesis is enhanced at DSBs, in a anner that depends on BLM and POLD3. Altogether our work unveils a role for BLM at DSBs in active chromatin, and highlights the toxic potential of RNA:DNA hybrids that accumulate at transcription-associated DSBs.