Biology subjects

Spindler, J.

Publications and source records attributed to Spindler, J..

4 recordsLinked to original sources

bioRxiv2025

SLX4IP acts in parallel to FANCM to limit BLM-dependent replication stress at ALT telomeres

Alternative Lengthening of Telomeres (ALT) is a telomerase-independent telomere maintenance mechanism that enables cancer cells to gain unlimited replicative capacity. ALT relies on recombination-mediated telomere elongation and is promoted by telomeric replication stress. However, ALT requires strict regulation, as excessive replication stress or recombination are cytotoxic. Central to ALT is the RecQ helicase BLM, which regulates telomeric replication stress and promotes telomere recombination and DNA synthesis. Despite its key role in the ALT pathway, BLM must be tightly regulated to prevent deleterious outcomes. Here, we identify SLX4IP as a key suppressor of BLM-driven replication stress at ALT telomeres. Loss of SLX4IP in ALT-positive cells leads to BLM-dependent telomeric replication stress and impaired replication fork progression. Mechanistically, SLX4IP limits the unwinding of unligated Okazaki fragments by BLM on the lagging strand during telomere replication. This reduces the formation of toxic 5' DNA flaps and prevents hyperactivation of ATR signalling and deleterious recombination levels. We also uncover a synthetic lethal interaction between SLX4IP and FANCM, an ATPase/translocase that is a known regulator of BLM at telomeric replication forks in ALT cells. We demonstrate that SLX4IP and FANCM act in parallel to restrain BLM activity, thereby maintaining the balance of replication stress and recombination that is necessary for productive ALT. These findings reveal a vulnerability in ALT-positive cancers lacking SLX4IP and establish SLX4IP as a potential biomarker for therapeutic strategies targeting FANCM. HIGHLIGHTSO_LISLX4IP depletion activates the replication stress response at ALT telomeres C_LIO_LISLX4IP acts in parallel to FANCM to limit replication stress at ALT telomeres C_LIO_LIThe synthetic lethal interaction between SLX4IP and FANCM is dependent on BLM C_LIO_LISLX4IP depletion causes BLM-dependent lagging-strand replication stress C_LI

cell biology↗

bioRxiv2024

HIV-1 control in vivo is related to the number but not the fraction of infected cells with viral unspliced RNA

In the absence of antiretroviral therapy (ART), a subset of individuals, termed HIV controllers, have levels of plasma viremia that are orders of magnitude lower than non-controllers who are at higher risk for HIV disease progression. In addition to having fewer infected cells resulting in fewer cells with HIV RNA, it is possible that lower levels of plasma viremia in controllers is due to a lower fraction of the infected cells having HIV-1 unspliced RNA (HIV usRNA) compared with non-controllers. To directly test this possibility, we used sensitive and quantitative single cell sequencing methods to compare the fraction of infected cells that contain one or more copies of HIV usRNA in peripheral blood mononuclear cells (PBMC) obtained from controllers and non-controllers. The fraction of infected cells containing HIV usRNA did not differ between the two groups. Rather, the levels of viremia were strongly associated with the total number of infected cells that had HIV usRNA, as reported by others, with controllers having 34-fold fewer infected cells per million PBMC. These results reveal for the first time that viremic control is not associated with a lower fraction of proviruses expressing HIV usRNA, unlike what is reported for elite controllers, but is only related to having fewer infected cells overall, maybe reflecting greater immune clearance of infected cells. Our findings show that proviral silencing is not a key mechanism for viremic control and will help to refine strategies towards achieving HIV remission without ART.

microbiology↗

bioRxiv2020

Early Emergence and Long-Term Persistence of HIV-Infected T Cell Clones in Children

Little is known about the emergence and persistence of HIV-infected T cell clones in perinatally-infected children. We analyzed peripheral blood mononuclear cells for clonal expansion in 11 children who initiated antiretroviral therapy (ART) between 1.8-17.4 months of age and with viremia suppressed for 6-9 years. We obtained 8,662 HIV-1 integration sites from pre-ART and 1,861 sites on ART. Expanded clones of infected cells were detected pre-ART in 10/11 children. In 8 children, infected cell clones detected pre-ART persisted for 6-9 years on ART. A comparison of integration sites in the samples obtained on ART with healthy donor PBMC infected ex-vivo showed selection for cells with proviruses integrated in BACH2 and STAT5B. Our analyses indicate that, despite marked differences in T cell composition and dynamics between children and adults, HIV-infected cell clones are established early in children, persist for up to 9 years on ART, and can be driven by proviral integration in proto-oncogenes.

microbiology↗

bioRxiv2018

Quantification of protein mobility and associated reshuffling of cytoplasm during chemical fixation

To understand cellular functionalities, it is essential to unravel spatio-temporal patterns of molecular distributions and interactions within living cells. The technological progress in fluorescence microscopy now allows in principle to measure these patterns with sufficient spatial resolution. However, high resolution imaging comes along with long acquisition times and high phototoxicity. Physiological live cell imaging is therefore often unfeasible and chemical fixation is employed. However, fixation methods have not been rigorously reviewed to preserve patterns at the resolution at which they can be nowadays imaged. A key parameter for this is the time span until fixation is completed. During this time, cells are under unphysiological conditions and patterns decay. We demonstrate here that formaldehyde fixation takes more than one hour for cytosolic proteins in cultured cells. Associated with this, we found a distinct displacement of proteins and lipids, including their loss from the cells. Other small aldehydes like glyoxal or acrolein showed inferior results. Fixations using glutaraldehyde were faster than four minutes and retained most cytoplasmic proteins. Surprisingly, autofluorescence produced by glutaraldehyde was almost completely antagonized by supplementary addition of formaldehyde without compromising fixation speed. These findings indicate, which cellular processes can actually be reliably imaged after a certain chemical fixation.

cell biology↗