Genome instability importantly contributing to transform normal cells to cancer cells with improved survival and proliferation rates. It remains unclear though how cancer cells overcome the huge burden arising from altered gene dosage, the consequence of genomic imbalance. Another mysterious characteristic of many cancers is the accumulation of mutations in their ribosomal protein (RP) genes. RPL5, RPL10 and RPL22 are mutated in ~20% of T-cell Acute Lymphoblastic Leukaemia (T-ALL) cases. In solid tumours including glioblastoma, breast cancer and melanoma, this number varies between 10% and 35%. RPL5 and RPL10 occupy neighbouring positions in the 60S subunit of the ribosomes, next to the central protuberance, which is in close vicinity to both the P, A, and E sites of the ribosomes. RPL10Arg98Ser mutation was shown to reduce translation fidelity. Numerous mechanisms with no clear consensus have mainly been considered in the literature to explain how RP mutations contribute to tumorigenesis or to tumour maintenance so far: global suppression of protein synthesis, specific suppression of protein synthesis, or extra-ribosomal functions. We discovered that Not1, the scaffold of the eukaryotic deadenylase Ccr4-Not complex is associating with RP encoding mRNAs in the nucleus and facilitates their translation in the cytoplasm. Interestingly, like RP genes CNOT3 a subunit of the Ccr4-Not complex also frequently mutated in cancers. It becomes inactivated in ~8% of adult T-ALL samples. We found that Not5, the yeast ortholog of CNOT3, facilitates nascent chain–chaperone interactions, and co-translational assembly of multi-protein complexes. Without Not5 assembly intermediates accumulate in the cytoplasm, often aggregating.
HYPOTHESIS AND AIMS:
Our hypothesis is that cancer cells cope with the deleterious effect of genomic imbalance by producing aggregated garbage instead of proteins and protein complexes whose overrepresentation would be toxic. Is it possible that mutations in CNOT3 and RP genes leads to the failure of co-translational folding and assembly processes in cancer cells? Is this gene expression regulatory misstep providing protection for cancer cells from their own toxic genome? We would like to find answers for these questions to reveal if the site of translation is a weak point of cancer cells or not. If proteins responsible for intrinsic barriers toward cancer are also aggregating, helping the folding of these proteins by liberating chaperone capacity from other processes might have the potential to awaken apoptotic pathways or to manifest the effect of the toxic gene dosage characteristic for many cancers. To achieve our goals, we plan to set up the following experimental strategies:
1. Identification of abundantly aggregating proteins in RP and Ccr4-Not mutant yeast and tumour cell line systems.
2. Analysis of protein aggregation in tumour samples from patients.
3. Studying the effect of non-essential abundant protein aggregation on viability of cancer cell lines.
Required language skills: English Further requirements: research work
Number of students who can be accepted: 1
Deadline for application: 2022-04-12
2024. IV. 17. ODT ülés Az ODT következő ülésére 2024. június 14-én, pénteken 10.00 órakor kerül sor a Semmelweis Egyetem Szenátusi termében (Bp. Üllői út 26. I. emelet).
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