Biology subjects

Escobar, E.

Publications and source records attributed to Escobar, E..

4 recordsLinked to original sources

bioRxiv2026

'Zipper' Grammar of CTD Governs the Spatial Programing of the Transcription Cycle of RNA Polymerase II

RNA polymerase II transcribes all protein-coding genes in eukaryotes, with its C-terminal domain (CTD) acting as a regulatory platform throughout the transcription cycle. Despite its simple sequence, the conserved heptad repeats encode a regulatory grammar critical for transcription initiation, elongation, and termination. Using structural analysis, single-molecule imaging, and synthetic CTD-engineered Pol II constructs, we defined the minimal sequence requirements across transcriptional stages. We show that while SP motifs are essential phosphorylation sites, flanking residues tolerate variability. In contrast, the periodic positioning of tyrosine residues is indispensable for pre-initiation complex (PIC) assembly through interactions with the Mediator, which are disrupted upon Ser5 phosphorylation triggering promoter escape. This supports a "zipper" model where sequential tyrosine engagement stabilizes PIC assembly and progressive phosphorylation propels Pol II escape. Site-specific Ser2/5 phosphorylation orchestrates 3-end processing factor recruitment. These findings redefine the functional grammar of the Pol II CTD and explain how a low-complexity sequence achieves regulatory specificity.

cell biology↗

bioRxiv2025

Non-mutated human tau stimulates Alzheimer's disease-relevant neurodegeneration in a microglia-dependent manner

The accumulation of abnormal, non-mutated tau protein is a key pathological hallmark of Alzheimers disease (AD). Despite its strong association with disease progression, the mechanisms by which tau drives neurodegeneration in the brain remain poorly understood. Here, we selectively expressed non-mutated or mutated human microtubule-associated protein tau (hMAPT) in neurons across the brain and observed neurodegeneration in the hippocampus, especially associated with non-mutated human tau. Single-nuclei RNA sequencing confirmed a selective loss of hippocampal excitatory neurons by the wild-type tau and revealed the upregulation of neurodegeneration-related pathways in the affected populations. The accumulation of phosphorylated tau was accompanied by cellular stress in neurons and reactive gliosis in multiple brain regions. Notably, the lifelong absence of microglia significantly and differentially influenced the extent of neurodegeneration in the hippocampus and thalamus. Therefore, our study established an AD-relevant tauopathy mouse model, elucidated both neuron-intrinsic and neuron-extrinsic responses, and highlighted critical and complex roles of microglia in modulating tau-driven neurodegeneration.

neuroscience↗

bioRxiv2019

The generality of post-antimicrobial treatment persistence of replicatively-attenuated Borrelia burgdorferi in a mouse model

A basic feature of infection caused by Borrelia burgdorferi, the etiological agent of Lyme borreliosis, is that persistent infection is the rule, not the norm, in its many hosts. The ability to persist and evade host immune clearance poses a challenge to effective antimicrobial treatment. A link between therapy failure and the presence of persister cells has started to emerge. There is growing experimental evidence that viable, but non-cultivable spirochetes persist following treatment with several different antimicrobial agents, then resurge after 12 months. The current study utilized the mouse model to evaluate if persistence and resurgence occur following antimicrobial treatment in a disease-susceptible (C3H/HeN) and disease-resistant (C57BL/6) mouse strain infected with B. burgdorferi strains N40 and B31, to confirm the generality of these phenomena. The status of infection was evaluated at 12 and 18-months after treatment. The results demonstrated that persistent spirochetes remain viable for up to 18 months following treatment, but divide slowly, thereby being tolerant to the effects of antimicrobial agents, as well as being non-cultivable. The phenomenon of persistence and resurgence in disease-susceptible C3H mice is equally evident in disease-resistant B6 mice, and not unique to any particular B. burgdorferi strain. The results also demonstrate that following antimicrobial treatment, both strains of B. burgdorferi, N40 and B31, lose one or more small plasmids, resulting in attenuation. The biological relevance of attenuated B. burgdorferi spirochetes is probably inconsequential. The study demonstrated that non-cultivable spirochetes can persist in a host following antimicrobial treatment for a long time but did not demonstrate their clinical relevance in a mouse model of chronic infection.

microbiology↗

bioRxiv2017

Arabidopsis HIPP27 is a host susceptibility gene for the beet cyst nematode Heterodera schachtii

SummarySedentary plant-parasitic cyst nematodes are obligate biotrophs that infect the roots of their host plant. Their parasitism is based on modification of root cells to form a hypermetabolic syncytium from which the nematodes draw their nutrients. The aim of this study was to identify nematode susceptibility genes in Arabidopsis thaliana and to characterize their roles in supporting the parasitism of Heterodera schachtii. By selecting genes that were most strongly upregulated in response to cyst nematode infection, we identified HIPP27 (HEAVY METAL-ASSOCIATED ISOPRENYLATED PLANT PROTEIN 27) as a host susceptibility factor required for beet cyst nematode infection and development. Detailed expression analysis revealed that HIPP27 is a cytoplasmic protein and that HIPP27 is strongly expressed in leaves, young roots and nematode-induced syncytia. Loss-of-function Arabidopsis hipp27 mutants exhibited severely reduced susceptibility to H. schachtii and abnormal starch accumulation in syncytial and peridermal plastids. Our results suggest that HIPP27 is a susceptibility gene in Arabidopsis whose loss-of-function reduces plant susceptibility to cyst nematode infection without increasing susceptibility to other pathogens or negatively affecting plant phenotype.

plant biology↗