Biology subjects

Majoros, H.

Publications and source records attributed to Majoros, H..

3 recordsLinked to original sources

bioRxiv2023

Cytoplasmic Aggregation of RPB1 Predicts Failure of Neoadjuvant Chemotherapy

We aimed to investigate the contribution of co-translational protein aggregation to the chemotherapy resistance of tumor cells. Increased co-translational protein aggregation reflects altered translation regulation that may have the potential to buffer transcription under genotoxic stress. As an indicator for such event, we followed cytoplasmic aggregation of RPB1, the aggregation prone largest subunit of RNA polymerase II, in biopsy samples taken from patients with invasive carcinoma of no special type. RPB1 frequently aggregates co-translationally in the absence of proper HSP90 chaperone function or in ribosome mutant cells as revealed formerly in yeast. We found that cytoplasmic foci of RPB1 occur in larger sizes in tumors that showed no regression after therapy. Based on these results, we propose that monitoring the cytoplasmic aggregation of RPB1 may be suitable for determining - from biopsy samples taken before treatment - the effectiveness of neoadjuvant chemotherapy.

cancer biology↗

bioRxiv2021

Old players in new posts: the role of P53, ATM and DNAPK in DNA damage-related ubiquitylation-dependent removal of S2P RNAPII

DNA double-strand breaks are the most deleterious lesions for the cells, therefore understanding the macromolecular interactions in the DNA repair-related mechanisms is essential. DNA damage triggers transcription silencing at the damage site, leading to the removal of the elongating RNA polymerase II (S2P RNAPII) from this locus, which provides accessibility for the repair factors to the lesion. Ataxia-telangiectasia mutated (ATM) and DNA-dependent protein kinase (DNAPK) are the two main regulatory kinases of homologous recombination and non-homologous end joining, respectively. Although these kinases are involved in the activation of different repair pathways, they have common target proteins, such as P53. We previously demonstrated that following transcription block, P53 plays a pivotal role in transcription elongation process by interacting with S2P RNAPII. In the current study, we reveal that P53, ATM and DNAPK are involved in the fine-tune regulation of the ubiquitin-proteasome system-related degradation of S2P RNAPII. However, they act differently in this process: P53 delays the removal of S2P RNAPII, while ATM and DNAPK participate in the activation of members of E3 ligase complexes involved in the ubiquitylation of S2P RNAPII. We also demonstrate that WW domain-containing protein 2 (WWP2) and Cullin-3 (CUL3) are interaction partners of S2P RNAPII, thus forming a complex with the transcribing RNAPII complex. Simple SummaryTo ensure the proper repair following DNA double-strand breaks, the eviction of the arrested elongating RNA polymerase II (S2P RNAPII) is required. Here, we report an emerging role of P53, Ataxia-telangiectasia mutated (ATM) and DNA-dependent protein kinase (DNAPK) in the ubiquitin-proteasome system-dependent removal of S2P RNAPII. We also identified interactions between S2P RNAPII and WW domain-containing protein 2 (WWP2) or Cullin-3 (CUL3) (members of E3 ligase complexes), which are involved in the ubiquitylation of S2P RNAPII following DNA damage. Furthermore, the RNAPII-E3 ligase complex interactions are mediated by P53, ATM and DNAPK, which suggests potential participation of all three proteins in the effective resolution of transcription block at the damage site. Altogether, our results provide a better comprehension of the molecular background of transcription elongation block-related DNA repair processes and highlight an indispensable function of P53, ATM and DNAPK in these mechanisms.

molecular biology↗

bioRxiv2019

Quantification of DNA damage induced γH2AX focus formation via super-resolution dSTORM localization microscopy

In eukaryotic cells, each process, in which DNA is involved, should take place in the context of chromatin structure. DNA double-strand breaks (DSBs) are one of the most deleterious damages often leading to chromosomal rearrangement. In response to environmental stresses, cells have developed repair mechanisms to eliminate the DSBs. Upon DSB induction, several factors play roles in chromatin relaxation by catalysing the appropriate histone posttranslational modification (PTM) steps, therefore promoting the access of the repair factors to the DSBs. Among these PTMs, the phosphorylation of the histone variant H2AX at its Ser139 residue (also known as {gamma}H2AX) could be observed at the break sites. The structure of {gamma}H2AX focus has to be organized during the repair as it contributes to accessibility of specific repair proteins to the damaged site. Our aim was to develop a quantitative approach to analyse the morphology of individual repair foci by super-resolution dSTORM microscopy to gain insight into genome organization in DNA repair. We have established a specific dSTORM measurement process by developing a new analytical algorithm for gaining quantitative information about chromatin morphology and repair foci topology at individual {gamma}H2AX enriched repair focus. By this method we quantified unique repair foci to show the average distribution of {gamma}H2AX clusters. By monitoring {gamma}H2AX signal, we could reach 20 nm spatial resolution and resolve a single DNA damage spot, which allow us to identify different chromatin sub-clusters around the break site. Additionally, based on our new analysis method, we were able to show the number of nucleosomes in each sub-cluster that could allow us to define the possible chromatin structure and the nucleosome density around the break sites. This method is the first demonstration of a single-cell based quantitative measurement of a discrete repair focus, which could provide new opportunities to categorize spatial organization of dot patterns by parametric determination of topological similarity.

cell biology↗