Biology subjects

Oravcova, M.

Publications and source records attributed to Oravcova, M..

4 recordsLinked to original sources

bioRxiv2025

SMC5/6-Mediated Plasmid Silencing is Directed by SIMC1-SLF2 and Antagonized by LT

SMC5/6 is unique amongst the Structural Maintenance of Chromosomes (SMC) complexes in its ability to repress transcription from extrachromosomal circular DNA (ecDNA), including viral genomes and plasmids. Previously, we showed that human SMC5/6 is regulated by two mutually exclusive subcomplexes--SIMC1-SLF2 and SLF1/2--the counterparts of yeast Nse5/6 (Oravcova, eLife, 2022). Notably, only SIMC1-SLF2 recruits SMC5/6 to SV40 Large T antigen (LT) foci in PML nuclear bodies (PML NBs), suggesting that these regulatory subcomplexes direct distinct roles of SMC5/6 on chromosomal versus ecDNA. However, their roles in plasmid repression remain unclear. Here, we demonstrate that SMC5/6-mediated repression of plasmid transcription depends exclusively on SIMC1-SLF2, whereas SLF1/2 is dispensable. Reinforcing its specialized role in ecDNA suppression, SIMC1-SLF2 does not participate in SMC5/6 recruitment to chromosomal DNA lesions. We further show that plasmid silencing requires a conserved interaction between SIMC1-SLF2 and SMC6, mirroring the functional relationship observed between yeast Nse5/6 and Smc6. As for viral silencing, plasmid repression depends on the SUMO pathway; however, unlike viral silencing, it does not require PML NBs. Additionally, we find that LT interacts with SMC5/6 and increases plasmid transcription to levels observed in SIMC1-SLF2-deficient cells-echoing the antagonistic roles of HBx (HBV) and Vpr (HIV-1) in viral genome repression. These findings expand the paradigm of viral antagonism against SMC5/6-mediated silencing, positioning LT as a novel player in this evolutionary tug-of-war.

cell biology↗

bioRxiv2023

Critical importance of DNA binding for CSL protein functions in fission yeast

CSL (CBF1/RBP-J{kappa}/Suppressor of Hairless/LAG-1) proteins are conserved transcription factors found in animals and fungi. In fission yeast, they regulate various cellular processes, including cell cycle progression, lipid metabolism, and cell adhesion. CSL proteins bind to DNA through their N-terminal Rel-like domain and central beta-trefoil domain. Here, we investigated the importance of DNA binding for CSL functions in the fission yeast Schizosaccharomyces pombe. We created CSL mutants with disrupted DNA binding and found that the vast majority of CSL functions depend on intact DNA binding. Specifically, DNA binding is crucial for the regulation of cell adhesion, lipid metabolism, cell cycle progression, long non-coding RNA expression, and genome integrity maintenance. Interestingly, perturbed lipid metabolism leads to chromatin structure changes, potentially linking lipid metabolism to the diverse CSL-associated phenotypes. Our study highlights the critical role of DNA binding for CSL protein functions in fission yeast. SUMMARY STATEMENTCSL transcription factors regulate a diverse set of processes, but the mechanisms are not always clear. We show that S. pombe CSL proteins need the ability to bind DNA for most of their roles.

molecular biology↗

bioRxiv2022

The Nse5/6-like SIMC1-SLF2 Complex Localizes SMC5/6 to Viral Replication Centers

The human SMC5/6 complex is a conserved guardian of genome stability and an emerging component of antiviral responses. These disparate functions likely require distinct mechanisms of SMC5/6 regulation. In yeast, Smc5/6 is regulated by its Nse5/6 subunits, but such regulatory subunits for human SMC5/6 are poorly defined. Here, we identify a novel SMC5/6 subunit called SIMC1 that contains SUMO interacting motifs (SIMs) and an Nse5-like domain. We isolated SIMC1 from the proteomic environment of SMC5/6 within polyomavirus large T antigen (LT)-induced subnuclear compartments. SIMC1 uses its SIMs and Nse5-like domain to localize SMC5/6 to polyomavirus replication centers (PyVRCs) at SUMO-rich PML nuclear bodies. SIMC1s Nse5-like domain binds to the putative Nse6 orthologue SLF2 to form an anti-parallel helical dimer resembling the yeast Nse5/6 structure. SIMC1-SLF2 structure-based mutagenesis defines a conserved surface region containing the N-terminus of SIMC1s helical domain that regulates SMC5/6 localization to PyVRCs. Furthermore, SLF1, which recruits SMC5/6 to DNA lesions, binds SLF2 analogously to SIMC1 and forms a distinct Nse5/6-like complex. Thus, two Nse5/6-like complexes independently regulate human SMC5/6: SIMC1-SLF2 responding to viral challenge and SLF1/2 recognizing DNA damage.

cell biology↗

bioRxiv2020

Activation of FAM111A Protease Induces Defects in Nuclear Function that Likely Underlie its Roles in Disease and Viral Restriction

Mutations in the nuclear trypsin-like serine protease FAM111A cause Kenny-Caffey syndrome (KCS2) with hypoparathyroidism and skeletal dysplasia, or perinatally lethal osteocraniostenosis (OCS). In addition, FAM111A was identified as a restriction factor for certain host range mutants of the SV40 polyomavirus and VACV orthopoxvirus. However, because FAM111A function is poorly characterized, its roles in restricting viral replication and the etiology of KCS2 and OCS remain undefined. We find that the FAM111A KCS2 and OCS patient mutants are hyperactive, inducing apoptosis-like phenotypes in a protease-dependent manner. Similarly, in response to the attempted replication of SV40 host range mutants in restrictive cells, FAM111A activity induces the loss of nuclear barrier function and structure. Interestingly, pan-caspase inhibitors do not block FAM111A-dependent phenotypes such as nuclear "leakiness", shrinkage and pore redistribution, implying it acts independently or upstream of caspases. In this regard, we identified nucleoporins and the associated GANP transcription factor as FAM111A interactors and candidate targets. Together our data provide key insight into how FAM111A activation can restrict viral replication, and how its deregulated activity could cause KCS2 and OCS.

cell biology↗