Biology subjects

Rooimans, M. A.

Publications and source records attributed to Rooimans, M. A..

4 recordsLinked to original sources

bioRxiv2026

Residual cohesin function and PARP1 levels determine PARP inhibitor sensitivity in STAG2-deficient cancers

The STAG1 and STAG2 paralogs are mutually exclusive subunits of cohesin, a large protein complex that controls different aspects of genome organization. Loss-of-function mutations in STAG2 are common in a variety of cancers, and have been associated with increased sensitivity to poly(ADP-ribose) polymerase inhibitors (PARPi). This provides a possible entry point for therapeutic exploitation. However, insights in the underlying mechanism and additional determinants of this sensitivity are currently lacking. Here we show that STAG2-deficient cell lines exhibit variable PARPi sensitivity. While wildtype TP53 enhances PARPi sensitivity in RPE1 cells, STAG2 depletion does not trigger p53 or affect PARPi sensitivity in RPE1-TP53wt cells. PARPi sensitivity is determined by the capacity of STAG1 to compensate for the lack of STAG2. It appears that STAG2 is not uniquely required for the PARPi response, and its loss predominantly sensitizes cells through a general defect in cohesin function. PARP trapping underlies this sensitivity and is strongly influenced by basal PARP1 expression levels and further enhanced by oncogenic signaling. Perturbations in sister chromatid cohesion also enhances PARPi sensitivity, correlating with aggravated cohesion defects and increased chromosome breakage. Mechanistically, cohesin impairment does not appear to compromise repair of nickase-induced DNA lesions, suggesting that cohesin-defective cells are particularly vulnerable to a distinct class of lesions associated with trapped PARP. Together, our findings identify residual cohesin function and PARP1 expression as key determinants of PARPi response and suggest that successful clinical application of PARP inhibitors in STAG2-mutant cancers will require biomarker-guided patient stratification rather than STAG2 mutation status alone.

molecular biology↗

bioRxiv2026

The SKA complex is a mitotic vulnerability of chromosomally unstable cancers

Aneuploidy and chromosomal instability are common characteristics of cancer but remain underexploited therapeutically. Because chromosomally unstable cells exhibit altered mitotic control, they are selectively vulnerable to inhibition of the kinesin KIF18A. Here, we identify the spindle and kinetochore-associated (SKA) complex as a mitotic regulator that establishes a similar dependency. SKA loss is tolerated in cells with a defective mitotic checkpoint, but when mitosis is prolonged, it leads to mitotic errors and loss of viability. Genetic analysis reveals that SKA and KIF18A are epistatic, although they function through mechanistically distinct mitotic pathways. SKA depletion selectively impacts chromosomally unstable cancer cells and mirrors the effects of KIF18A inhibition. We thus identify a cellular vulnerability associated with prolonged mitosis in chromosomally unstable cancers.

cell biology↗

bioRxiv2022

CRISPR screens in sister chromatid cohesion defective cells reveal PAXIP1-PAGR1 as regulator of chromatin association of cohesin

The cohesin complex regulates higher order chromosome architecture through maintaining sister chromatid cohesion and folding chromatin by active DNA loop extrusion. Impaired cohesin function underlies a heterogeneous group of genetic syndromes and is associated with cancer. Here, by using synthetic lethality CRISPR screens in isogenic human cell lines defective of specific cohesion regulators, we mapped the genetic dependencies induced by absence of DDX11 or ESCO2. The obtained high confidence synthetic lethality networks are strongly enriched for genes involved in DNA replication and mitosis and support the existence of parallel sister chromatid cohesion establishment pathways. Among the hits, we identified the chromatin binding, BRCT-domain containing protein PAXIP1 as a novel cohesin regulator. Depletion of PAXIP1 severely aggravated cohesion defects in ESCO2 defective cells, leading to mitotic cell death. PAXIP1 promoted the global chromatin association of cohesin, independent of DNA replication, a function that could not be explained by indirect effects of PAXIP1 on transcription or the DNA damage response. Cohesin regulation by PAXIP1 required its binding partner PAGR1 and a conserved FDF motif in PAGR1. Similar motifs were previously found in multiple cohesin regulators, including CTCF, to mediate physical interactions with cohesin. PAXIP1 co-localizes with cohesin on multiple genomic loci, including at active gene promoters and enhancers. Together, this study identifies the PAXIP1-PAGR1 complex as a novel regulator of cohesin occupancy on chromatin. Possibly, this role in cohesin regulation is also relevant for previously described functions of PAXIP1 in transcription, immune cell maturation and DNA repair.

molecular biology↗

bioRxiv2019

Non-Redundant Roles in Sister Chromatid Cohesion of the DNA Helicase DDX11 and the SMC3 Acetyl Transferases ESCO1/2

In a process linked to DNA replication, duplicated chromosomes are co-entrapped into large, circular cohesin complexes and functional sister chromatid cohesion (SCC) is established by acetylation of the SMC3 cohesin subunit. Several rare human developmental syndromes are characterized by defective SCC. Roberts Syndrome (RBS) is caused by mutations in the SMC3 acetyl transferase ESCO2, whereas mutations in the DNA helicase DDX11 lead to Warsaw Breakage Syndrome (WABS). We found that WABS-derived cells predominantly rely on ESCO2, not ESCO1, for residual SCC, growth and survival. Reciprocally, RBS-derived cells depend on DDX11 to maintain low levels of SCC. Synthetic lethality between DDX11 and ESCO2 correlated with a prolonged delay in mitosis, and was rescued by knock down of the cohesion remover WAPL. Rescue experiments using mouse or human cDNAs revealed that DDX11, ESCO1 and ESCO2 act on differential aspects of DNA replication-coupled SCC establishment. Importantly, DDX11 is required for normal DNA replication fork speed without clearly affecting SMC3 acetylation. We propose that DDX11 and ESCO2 control spatially separated fractions of cohesin, with supportive roles for DDX11 in replication-associated cohesion establishment, and for ESCO2 in cohesin complexes located around centromeres, respectively.

cell biology↗