Biology subjects

Muller, P.

Publications and source records attributed to Muller, P..

5 recordsLinked to original sources

bioRxiv2024

Epigenetic histone modifications H3K36me3 and H4K5/8/12/16ac induce open polynucleosome conformations via different mechanisms

Nucleosomes are the basic compaction unit of chromatin and nucleosome structure, and their higher-order assemblies regulate genome accessibility. Many post-translational modifications alter nucleosome dynamics, nucleosome-nucleosome interactions, and ultimately chromatin structure and gene expression. Here, we investigate the role of two post-translational modifications associated with actively transcribed regions, H3K36me3 and H4K5/8/12/16ac, in the contexts of tri-nucleosome arrays that provide a tractable model system for quantitative single-molecule analysis, while enabling us to probe nucleosome-nucleosome interactions. Direct visualization by AFM imaging reveals that H3K36me3 and H4K5/8/12/16ac nucleosomes adopt much more open and loose conformations than unmodified nucleosomes. Similarly, magnetic tweezers force spectroscopy shows a reduction in DNA outer turn wrapping and nucleosome-nucleosome interactions for the modified nucleosomes. The results suggest that for H3K36me3 the increased breathing and outer DNA turn unwrapping seen in mononucleosomes propagates to more open conformations in nucleosome arrays. In contrast, the even more open structures of H4K5/8/12/16ac nucleosome arrays do not appear to derive from the dynamics of the constituent mononucleosomes, but are driven by reduced nucleosome-nucleosome interactions, suggesting that stacking interaction can overrule DNA breathing of individual nucleosomes. We anticipate that our methodology will be broadly applicable to reveal the influence of other post-translational modifications and action of nucleosome remodelers.

biophysics↗

bioRxiv2021

Ultraviolet light-induced collagen degradation inhibits melanoma invasion

Ultraviolet radiation (UVR) increases the incidence of cutaneous melanoma1-4. The ageing, sun-exposed dermis accumulates UVR damage5, and older patients develop more melanomas at UVR-exposed sites4,6,7. As fibroblasts are functionally heterogeneous and play key roles in the stromal contribution to cancer8,9, we asked whether UVR modifies dermal fibroblast function. Here we confirmed the expression of collagen-cleaving matrix metalloprotein-1 (MMP1) by UVR-damaged fibroblasts was persistently upregulated to reduce local levels of collagen 1 (COL1A1), and found dermal COL1A1 degradation by MMP1 decreased melanoma invasion. Conversely, we show inhibiting extracellular matrix degradation and MMP1 expression restored melanoma invasion to UVR damaged dermis. We confirmed in vitro findings in a cohort of primary cutaneous melanomas of aged humans, showing more cancer cells invade as single cells at the invasive front of melanomas expressing and depositing more collagen. We found collagen and single melanoma cell invasion are robust predictors of poor melanoma-specific survival. These data indicate melanomas arising over UVR-damaged, collagen-poor skin of the elderly are less invasive, and this reduced invasion improves survival. Consequently, although UVR increases tumour incidence, it delays primary melanoma invasion by degrading collagen. However, we show melanoma-associated fibroblasts can restore invasion in low-collagen primary tumours by increasing collagen synthesis. Finally, we demonstrate high COL1A1 gene expression is a biomarker of poor outcome across a broad range of primary cancers.

cancer biology↗

bioRxiv2019

RecA influences biofilm development in the opportunistic pathogen Acinetobacter baumannii

Infections caused by Acinetobacter baumannii, a Gram-negative opportunistic pathogen, are difficult to eradicate due to the bacteriums propensity to quickly gain antibiotic resistances and form biofilms, a protective bacterial multicellular community. The A. baumannii DNA damage response (DDR) mediates the antibiotic resistance acquisition and regulates RecA in an atypical fashion; both RecALow and RecAHigh cell types are formed in response to DNA damage. The findings of this study demonstrate that the levels of RecA can influence the development, formation and dispersal, of biofilms through the global biofilm regulator bfmR. RecA loss results in surface attachment and prominent biofilms, while elevated RecA leads to diminished attachment and dispersal. These findings suggest that the challenge to treat A. baumannii infections may be explained by the induction of the DDR, common during infection, as well as the delicate balance between maintaining biofilms in low RecA cells, and promoting mutagenesis and dispersal in high RecA cells. This study underscores the importance of understanding the fundamental biology of bacteria to develop more effective treatments for infections.

microbiology↗

bioRxiv2019

EML4-ALK V3 drives cell migration through NEK9 and NEK7 kinases in non-small-cell lung cancer

EML4-ALK is an oncogenic fusion present in [~]5% lung adenocarcinomas. However, distinct EML4-ALK variants differ in the length of the EML4 microtubule-associated protein encoded within the fusion and are associated with a poorly understood variability in disease progression and therapeutic response. Here, we show that EML4-ALK variant 3, which is linked to accelerated metastatic spread and worse patient outcome, causes microtubule stabilization, formation of extended cytoplasmic protrusions, loss of cell polarity and increased cell migration. Strikingly, this is dependent upon the NEK9 kinase that interacts with the N-terminal region of EML4. Overexpression of wild-type EML4, as well as constitutive activation of NEK9, also perturbs cell morphology and accelerates cell migration in a manner that requires the downstream kinase NEK7 but not ALK activity. Moreover, elevated NEK9 is associated in patients with EML4-ALK V3 expression, as well as reduced progression-free and overall survival. Hence, we propose that EML4-ALK V3 promotes microtubule stabilization through recruitment of NEK9 and NEK7 to increase cell migration and that this represents a novel actionable pathway that drives disease progression in lung cancer.

cancer biology↗

bioRxiv2017

Paternal grandparental exposure to crop failure or surfeit during a childhood slow growth period and epigenetic marks on third generational growth-, glucoregulatory and stress genes

This latest in our series of papers describes transgenerational methylation related to midchildhood food availability in 19th century Overkalix, Sweden. Failed vs. bountiful crops differentially influenced methylation in grandchildren of paternal grandparents exposed to feast or famine during their Slow Growth Period (SGP), a sensitive period preceding the pre-pubertal growth spurt. In this case-study of 8 tracked 75-year old progeny with differential ancestral exposure, we found, in 40 posited gene ontology pathways, 39 differentially methylated CpG regions (DMRs) related to famine, excess food and food-insecurity stress, 9 of which with DMRs above 5%. Three gene ontology terms (GOs) \"insulin processing\", \"adipose development\" and \"hypothalamus development\" were key, with DMRs >14%. An unbiased test of known pathways revealed four nuclear transcription factors upstream of promotors repressing the pathway following paternal grandparental famine experience, as well as 4 upregulated GOs with average DMRs >20%. We conclude that this is the first demonstration of human transgenerational inheritance of epigenetic marks following ancestral childhood exposure to variable food availability inducing early developmental origins of adult disease.

genomics↗