Biology subjects

Puustinen, M. C.

Publications and source records attributed to Puustinen, M. C..

4 recordsLinked to original sources

bioRxiv2024

Dynamic HSF2 regulation drives breast cancer progression by steering the balance between proliferation and invasion

Phenotypic plasticity is a hallmark of breast carcinogenesis that facilitates the acquisition of invasive properties via epithelial-mesenchymal transition (EMT). Transforming growth factor-beta (TGF-{beta}), a key EMT-inducing cytokine, drives pro-metastatic gene programs through downstream transcription factors. Among mammalian stress-protective transcription factors, heat shock factor 2 (HSF2) has been associated with cancer progression, but the mechanisms regulating HSF2 expression and activity are unknown. Here, we demonstrate that TGF-{beta} stimulation downregulates HSF2 to enable activation of an invasive phenotype. Remarkably, ectopic expression of HSF2 in breast cancer cells inhibited TGF-{beta}-mediated effects on gene expression and cellular properties. By using both in vitro cell models and in vivo zebrafish xenografts, we found that a temporal downregulation of HSF2 is a prerequisite for EMT activation, while ectopically sustained HSF2 promotes rapid cell proliferation and survival. Analyses of human patient tissues corroborated our results by showing that HSF2 is dynamically regulated during breast cancer progression. Specifically, HSF2 expression and nuclear co-localization with the proliferation marker Ki67 are dramatically increased already in ductal carcinoma in situ. Altogether, our findings expand the pathological landscape of HSF2, demonstrating that dynamic regulation of HSF2 is an inherent property of malignant progression and characterizes the distinct stages of breast cancer.

cell biology↗

bioRxiv2022

A subpopulation of Talin 1 resides in the nucleus and regulates gene expression

Talin 1 (TLN1) is best known for its role at focal adhesions, where it activates {beta}-integrin receptors and transmits mechanical stimuli to the actin cytoskeleton. Interestingly, the localization of TLN1 is not restricted to the focal adhesions, but its function in other cellular compartments remains poorly understood. By utilizing both biochemical and confocal microscopy analyses, we show that TLN1 localizes to the nucleus and that it strongly interacts with the chromatin. Importantly, depletion of endogenous TLN1 results in extensive changes in the gene expression profile of human breast epithelial cells. To determine the impact of nuclear TLN1 on gene regulation, we expressed a TLN1 fusion protein containing a nuclear localization signal. Our results revealed that nuclear TLN1 regulates a specific subset of the TLN1-dependent genes. Taken together, we show that apart from localizing at the plasma membrane and cytoplasm, TLN1 also resides in the nucleus where it functions in the regulation of gene expression.

molecular biology↗

bioRxiv2021

HSFs drive stress type-specific transcription of genes and enhancers

Reprogramming of transcription is critical for the survival under cellular stress. Heat shock has provided an excellent model to investigate nascent transcription in stressed cells, but the molecular mechanisms orchestrating RNA synthesis during other types of stress are unknown. We utilized PRO-seq and ChIP-seq to study how Heat Shock Factors, HSF1 and HSF2, coordinate transcription at genes and enhancers upon oxidative stress and heat shock. We show that pause-release of RNA polymerase II (Pol II) is a universal mechanism regulating gene transcription in stressed cells, while enhancers are activated at the level of Pol II recruitment. Moreover, besides functioning as conventional promoter-binding transcription factors, HSF1 and HSF2 bind to stress-induced enhancers to trigger Pol II pause-release from poised gene promoters. Importantly, HSFs act at distinct genes and enhancers in a stress type-specific manner. HSF1 binds to many chaperone genes upon oxidative and heat stress but activates them only in heat-shocked cells. Under oxidative stress, HSF1 and HSF2 trans-activate genes independently of each other, demonstrating, for the first time, that HSF2 is a bona fide transcription factor. Taken together, we show that HSFs function as multi-stress-responsive factors that activate specific genes and enhancers when encountering changes in temperature and redox state.

molecular biology↗

bioRxiv2018

CBP/EP300-dependent acetylation and stabilization of HSF2 are compromised in the rare disorder, Rubinstein-Taybi syndrome

Cells respond to protein-damaging insults by activating heat shock factors (HSFs), key transcription factors of proteostasis. Abnormal HSF protein levels occur in cancer and neurodegenerative disorders, highlighting the importance of the tight control of HSF expression. HSF2 is a short-lived protein, but it is abundant in the prenatal brain cortex and required for brain development. Here, we reveal that HSF2 is acetylated and co-localized with the lysine-acetyl transferases CBP and EP300 in human brain organoids. Using unbiased, biochemical, cell-imaging, and in silico approaches, we show that CBP/EP300 acetylates HSF2 at specific lysine residues, which promotes HSF2 stabilization, whereas the lysine deacetylase HDAC1 catalyzes its proteasomal degradation. The CBP KIX domain and KlX-recognizing motifs in HSF2 are critical for its interaction with acetylating enzymes. The functional importance of acetylated HSF2 is evidenced in Rubinstein-Taybi syndrome (RSTS), characterized by mutated CBP or EP300. We show that RSTS patient cells exhibit decreased HSF2 levels and impaired heat shock response. The dysregulated HSF pathway in RSTS opens new avenues for understanding the molecular basis of this multifaceted pathology.

developmental biology↗