Biology subjects

Maria, H.

Publications and source records attributed to Maria, H..

3 recordsLinked to original sources

bioRxiv2025

Longitudinal Imaging of the Premalignant Tumor Microenvironment Reveals Transient Myeloid States Predictive of Tumor Fate

The spontaneous regression of cancer lesions illustrates the power of immune surveillance; yet these transient events have largely escaped systematic analysis. Using longitudinal intravital microscopy in a carcinogen-induced model of head and neck cancer, we followed premalignant lesions within the same animals for 24 weeks at single-cell resolution. This strategy uncovered three trajectories: progression, stability, or regression, and enabled direct analysis of immune dynamics underlying each fate. Lesion outcome was determined by the spatial organization of myeloid-derived antigen-presenting cells: regressing lesions were characterized by dense clusters of myeloid-derived cells associated with CXCL9+/CXCL10+ expression and T cell recruitment, whereas progressing lesions displayed a scattered infiltration of these cells. Remarkably, transient myeloid clusters arose prior to any detectable lesion formation and marked regions that would later develop into premalignant lesions. These findings identify spatiotemporal myeloid organization as an early determinant of tumor fate and provide a mechanistic framework for predicting and intercepting cancer at its inception. Summary SentenceEarly myeloid architecture dictates cancer fate: dense CXCL9/CXCL10 clusters with T-cell enrichment accompany regression, whereas sparse infiltration predicts progression. Transient pre-lesional myeloid clusters emerge at future tumor sites, revealing immune organization as an early determinant of malignancy.

cancer biology↗

bioRxiv2022

The DNA replication protein Orc1 from the yeast Torulaspora delbrueckii is required for heterochromatin formation but not as a silencer-binding protein

To understand the process by which new protein functions emerge, we examined how the yeast heterochromatin protein Sir3 arose through gene duplication from the conserved DNA replication protein Orc1. Orc1 is a subunit of the origin recognition complex (ORC), which marks origins of DNA replication. In Saccharomyces cerevisiae, Orc1 also promotes heterochromatin assembly by recruiting the structural proteins Sir1-4 to silencer DNA. In contrast, the paralog of Orc1, Sir3, is a nucleosome-binding protein that spreads across heterochromatic loci in conjunction with other Sir proteins. We previously found that a non-duplicated Orc1 from the yeast Kluyveromyces lactis behaved like ScSir3 but did not have a silencer-binding function like ScOrc1. Moreover, K. lactis lacks Sir1, the protein that interacts directly with ScOrc1. Here, we searched for the presumed intermediate state in which non-duplicated Orc1 possesses both the silencer-binding and spreading functions. In the non-duplicated species Torulaspora delbrueckii, which has an ortholog of Sir1 (TdKos3), we found that TdOrc1 spreads across heterochromatic loci independently of ORC, as ScSir3 and KlOrc1 do. This spreading is dependent on the nucleosome binding BAH domain of Orc1 and on Sir2 and Kos3. However, TdOrc1 does not have a silencer-binding function: T. delbrueckii silencers do not require ORC binding sites to function, and Orc1 and Kos3 do not appear to interact. Instead, Orc1 and Kos3 both spread across heterochromatic loci with other Sir proteins. Thus, Orc1 and Sir1/Kos3 originally had different roles in heterochromatin formation than they do now in S. cerevisiae.

genetics↗

bioRxiv2019

The NAD+-dependent deacetylase Sir2 enables evolution of new traits by regulating distinct gene sets in two yeast species, Saccharomyces cerevisiae and Kluyveromyces lactis

Evolutionary adaptation increases the fitness of an organism in its environment. It can occur through rewiring of gene regulatory networks, such that an organism responds appropriately to environmental changes. We investigated whether sirtuin deacetylases, which repress transcription and require NAD+ for activity, could facilitate the evolution of potentially adaptive responses by serving as transcriptional rewiring points. If so, bringing genes under the control of sirtuins could enable organisms to mount appropriate responses to stresses that decrease NAD+ levels. To explore how the genomic targets of sirtuins shift over evolutionary time, we compared two yeast species, Saccharomyces cerevisiae and Kluyveromyces lactis that display differences in cellular metabolism and lifecycle timing in response to nutrient availability. We identified sirtuin-regulated genes through a combination of chromatin immunoprecipitation and RNA expression. In both species, regulated genes were associated with NAD+ homeostasis, mating, and sporulation, but the specific genes differed. In addition, regulated genes in K. lactis were associated with other processes, including utilization of non-glucose carbon sources, heavy metal efflux, DNA synthesis, and production of the siderophore pulcherrimin. Consistent with the species-restricted regulation of these genes, sirtuin deletion impacted relevant phenotypes in K. lactis but not S. cerevisiae. Finally, sirtuin-regulated gene sets were depleted for broadly-conserved genes, consistent with sirtuins regulating processes restricted to a few species. Taken together, these results are consistent with the notion that sirtuins serve as rewiring points that allow species to evolve distinct responses to low NAD+ stress.

evolutionary biology↗