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Phosphoric acid fuel cells (PAFCs) not only generate electricity but also produce a substantial amount of waste heat. This study introduces a novel conceptual framework that integrates a PAFC, a gas turbine, and a waste heat recovery unit to provide combined cooling, heating, and power (CCHP) services for various applications. The system's operational versatility is achieved by manipulating valve openings, allowing for the regulation of waste heat utilization across six distinct operational modes. A thermodynamic model has been developed and validated to evaluate system performance under diverse design conditions and configurations.A comprehensive analysis examines the impact of key variables on system metrics, including efficiency, exergy, and economic performance. Additionally, the analysis assesses system exergy losses and economic viability, revealing that the PAFC module experiences the highest energy loss, followed by the ARS and ORC, while the DHW exhibits the lowest relative losses. Furthermore, the economic evaluation underscores the system's adaptability, suggesting that it is a potentially viable option for CCHP production.

Cells trigger the assembly of stress granules (SGs) under various stress conditions. Among the many proteins recruited to SGs are RNA-binding proteins and transcription regulators. Here, we report the translocation of human (h)Cdc73, a component of the PAF1 transcription complex, to cytosolic SGs in response to arsenic stress. The hCdc73 protein possesses a long intrinsically disordered region (IDR) from amino acids 256-416, the presence of which is required for the translocation of hCdc73 to cytosolic SGs. The purified hCdc73 IDR formed droplets in vitro, and the light-activated assembly of hCdc73-IDR-mCherry-CRY2 was verified. For translocation of hCdc73 to SGs, physical interactions with SG carrier proteins, such as FMR1, are also needed. Previously, we reported that the cytosolic hCdc73-eEF1Bγ complex controls the stability of p53 mRNA. Under arsenic stress, selective sequestration of cytosolic hCdc73, but not eEF1Bγ (EEF1G) or p53 (TP53) mRNA, was detected. As a result, a transient increase in p53 mRNA at the post-transcriptional level was observed. In conclusion, we propose that the availability of mRNAs for stress-responsive genes can be controlled by restraining their negative regulators within SGs. [ABSTRACT FROM AUTHOR]

Dredged sediment has high water content, and its engineering characteristics are poor; therefore, the treatment and disposal of dredged sediment is difficult, and the utilization efficiency of these resources is low. Various methods can be used to dehydrate dredged sediment, among which flocculation dewatering is the most widely used. In this study, the basic properties of dredged sediment were examined, and the flocculation dehydration effect of dredged sediment was analyzed in relation to the polyaluminum ferric chloride (PAFC) dosage, water content, and time. There is an optimal flocculant dosage added during dredged sediment processing. Dredged sediment with high water content has obvious flocculation effect. Flocculant can speed up the flocculation dehydration of dredged sediment in a short time, but long-term dehydration has no advantages compared with natural dredged sediment; the dehydration effect was even weaker than that of natural dredged sediment dehydration in the later stages of sedimentation. Meanwhile, this paper divided the settling process into different stages; the settlement coefficients and compaction settlement indexes in different settling stages can well reflect the flocculating performance of flocculants at each settling stage. [ABSTRACT FROM AUTHOR]

Microplastics in surface water and groundwater are posing significant risks to both ecological systems and human health. Conventional coagulants are limited in their efficacy for microplastic removal and may potentially lead to secondary pollution. The present study investigated the effectiveness of Opuntia Milpa Alta (OMA) particles, as a natural coagulant, in combination with polyaluminum ferric chloride (PAFC) to remove polystyrene (PS) microplastics. The results demonstrated the pivotal role of OMA in facilitating the coagulation. Specifically, the combination of 15 mg/L of OMA and 30 mg/L of PAFC achieved a removal rate of 94.8 %. Zeta potential analysis, scanning electron microscopy (SEM) characterization, and Fourier transform infrared spectroscope (FTIR) analysis revealed that the promotion mechanisms by OMA primarily involved charge neutralization and adsorption bridging, attributed to the presence of polygalacturonic acid from OMA's mucilage, the rough surface and the mesh structures of OMA. Influences of Cl−, SO 4 2− and HCO 3 − within the concentration range found in surface and groundwater were also studied. Furthermore, a cost assessment demonstrated that the incorporation of OMA not only enhanced the coagulation performance but also reduced overall costs. These findings will provide valuable insights towards the development of cost-effective techniques for the removal of microplastics from water. [Display omitted] • OMA promoted the removal of PS microplastics significantly in combination with PAFC. • The promotion mechanisms involved charge neutralization and adsorption bridging. • The coagulation process was found to be most effective under alkaline conditions. • Particle size of OMA could influence the coagulation performance. • Incorporation of OMA with PAFC could reduce the overall costs. [ABSTRACT FROM AUTHOR]

Objectives Mycobacterium tuberculosis (MTB), the causative agent of tuberculosis (TB), can survive inside the host granuloma courtesy the various extrinsic and intrinsic factors involved. Continuous use or misuse of the anti TB drugs over the years has led to the development of resistance in MTB against antibiotics. Drug-resistant TB in particular has been a menace since treating it requires exposing the patient to drugs for a prolonged period of time. Multidrug-resistant (MDR) and extensively drug resistant TB cases have increased over the years mostly due to the exposure of MTB to suboptimal levels of drug. Proteasomes provide MTB its pathogenicity and hence helps it to survive inside the host even in the presence of drugs. Materials and Methods The recombinantly expressed proteasome accessory factor-C (PafC) protein was purified via Ni-NTA affinity chromatography and overexpressed in the nonpathogenic strain of mycobacteria (Mycobacterium smegmatis) for the comparative analysis of minimum inhibitory concentrations of antimycobacterial drugs. The bacteria were subjected to various stress conditions. Secretory nature of PafC was analyzed by probing the purified protein against patient sera. Quantitative mRNA analysis of pafC, lexA, and recA was performed to check for their level under fluoroquinolone (FQ) presence. The data were validated in clinical samples of pulmonary TB patients. Results pafC, that forms one part of paf operon, is involved in providing MTB its resistance against FQs. Through a series of experiments, we established the fact that PafC is upregulated in mycobacteria upon exposure to FQs and it leads to the increased intracellular survival of mycobacteria under the stresses generated by FQs. The study also refers to the correlation of pafC to deoxyribonucleic acid (DNA) damage repair enzymes lexA and recA at transcriptional level. The results obtained in vitro corroborated when the pulmonary TB patients’ samples were subjected to the same molecular analysis. Statistical Analysis All experiments were conducted at least in triplicate. p-Value of

Fe–Al based flocculants (PAFC) have been widely used in sewage treatment. In this article, a new method for preparing PAFC from red mud was proposed, the magnetic product was upgraded and "downgrading Fe of red mud" was obtained based on a microwave selective carbothermic reduction and magnetic separation technique. The results showed that the Fe and Al contents in "downgrading Fe of red mud" were determined to be 24.60% and 22.27%, respectively. The Fe and Al digestion rates of "downgrading Fe of red mud" were 81.24% and 28.55% during the preparation of PAFC, respectively. The prepared PAFC can effectively achieve the effect of sewage treatment, and the turbidity removal rate of sewage reached 88.17%. In addition, microwave can realize rapid reduction at low temperature, and the magnetite obtained by magnetic separation can be used in the iron‐making process to realize the recycling of resources. [ABSTRACT FROM AUTHOR]

Objectives   Mycobacterium tuberculosis (MTB), the causative agent of tuberculosis (TB), can survive inside the host granuloma courtesy the various extrinsic and intrinsic factors involved. Continuous use or misuse of the anti TB drugs over the years has led to the development of resistance in MTB against antibiotics. Drug-resistant TB in particular has been a menace since treating it requires exposing the patient to drugs for a prolonged period of time. Multidrug-resistant (MDR) and extensively drug resistant TB cases have increased over the years mostly due to the exposure of MTB to suboptimal levels of drug. Proteasomes provide MTB its pathogenicity and hence helps it to survive inside the host even in the presence of drugs. Materials and Methods  The recombinantly expressed proteasome accessory factor-C (PafC) protein was purified via Ni-NTA affinity chromatography and overexpressed in the nonpathogenic strain of mycobacteria (Mycobacterium smegmatis) for the comparative analysis of minimum inhibitory concentrations of antimycobacterial drugs. The bacteria were subjected to various stress conditions. Secretory nature of PafC was analyzed by probing the purified protein against patient sera. Quantitative mRNA analysis of paf C, lex A, and rec A was performed to check for their level under fluoroquinolone (FQ) presence. The data were validated in clinical samples of pulmonary TB patients. Results   pafC , that forms one part of paf operon, is involved in providing MTB its resistance against FQs. Through a series of experiments, we established the fact that PafC is upregulated in mycobacteria upon exposure to FQs and it leads to the increased intracellular survival of mycobacteria under the stresses generated by FQs. The study also refers to the correlation of pafC to deoxyribonucleic acid (DNA) damage repair enzymes lexA and recA at transcriptional level. The results obtained in vitro corroborated when the pulmonary TB patients' samples were subjected to the same molecular analysis. Statistical Analysis  All experiments were conducted at least in triplicate. p -Value of <0.05 was considered to be statistically significant Conclusion  PafC plays a significant role in providing resistance to mycobacteria against FQ class of drugs by increasing its intracellular survival through increased drug efflux and getting involved with DNA damage repair machinery. [ABSTRACT FROM AUTHOR]

Small, cysteine-rich and cationic antimicrobial proteins (AMPs) from filamentous ascomycetes promise treatment alternatives to licensed antifungal drugs. In this study, we characterized the Penicillium chrysogenum Q176 antifungal protein C (PAFC), which is phylogenetically distinct to the other two Penicillium antifungal proteins, PAF and PAFB, that are expressed by this biotechnologically important ascomycete. PAFC is secreted into the culture broth and is co-expressed with PAF and PAFB in the exudates of surface cultures. This observation is in line with the suggested role of AMPs in the adaptive response of the host to endogenous and/or environmental stimuli. The in silico structural model predicted five β-strands stabilized by four intramolecular disulfide bonds in PAFC. The functional characterization of recombinant PAFC provided evidence for a promising new molecule in anti-Candida therapy. The thermotolerant PAFC killed planktonic cells and reduced the metabolic activity of sessile cells in pre-established biofilms of two Candidaalbicans strains, one of which was a fluconazole-resistant clinical isolate showing higher PAFC sensitivity than the fluconazole-sensitive strain. Candidacidal activity was linked to severe cell morphology changes, PAFC internalization, induction of intracellular reactive oxygen species and plasma membrane disintegration. The lack of hemolytic activity further corroborates the potential applicability of PAFC in clinical therapy. [ABSTRACT FROM AUTHOR]

In this paper, a phosphoric acid fuel cell integrated with reformer and evaporator is demonstrated. Oxidative steam reforming of methanol (OSRM) process is employed in this system in cooperated with a high efficient evaporator, and the reacted gas is sent into a phosphorus-acid fuel cell (PAFC) for direct power generation after surplus methanol/water filtration. The results show that the maximum power density of this hybrid system achieves 277 mW/cm2 without CO 2 removal, while it achieves 485 mW/cm2 when employing pure hydrogen as the fuel. Image 1 • A phosphoric acid fuel cell integrated with reformer and evaporator is demonstrated. • OSRM Reformer including a high efficient evaporator. • The maximum power density of this system achieves 277 mW/cm2 without CO 2 removal. [ABSTRACT FROM AUTHOR]

Small, cysteine-rich and cationic antimicrobial proteins (AMPs) from filamentous ascomycetes promise treatment alternatives to licensed antifungal drugs. In this study, we characterized the Penicillium chrysogenum Q176 antifungal protein C (PAFC), which is phylogenetically distinct to the other two Penicillium antifungal proteins, PAF and PAFB, that are expressed by this biotechnologically important ascomycete. PAFC is secreted into the culture broth and is co-expressed with PAF and PAFB in the exudates of surface cultures. This observation is in line with the suggested role of AMPs in the adaptive response of the host to endogenous and/or environmental stimuli. The in silico structural model predicted five β-strands stabilized by four intramolecular disulfide bonds in PAFC. The functional characterization of recombinant PAFC provided evidence for a promising new molecule in anti-Candida therapy. The thermotolerant PAFC killed planktonic cells and reduced the metabolic activity of sessile cells in pre-established biofilms of two Candidaalbicans strains, one of which was a fluconazole-resistant clinical isolate showing higher PAFC sensitivity than the fluconazole-sensitive strain. Candidacidal activity was linked to severe cell morphology changes, PAFC internalization, induction of intracellular reactive oxygen species and plasma membrane disintegration. The lack of hemolytic activity further corroborates the potential applicability of PAFC in clinical therapy.

Benthic Oscillatoria sp. may form dense surface blooms especially under eutrophic and calm conditions, which poses a threat to drinking water safety because it can produce toxic and odorous metabolites. This is the first study to investigate the effect of the conventional coagulant polyaluminium ferric chloride (PAFC) on removal of Oscillatoria sp., and the behavior of Oscillatoria sp. cells in sludges formed from different dosages of PAFC (control, optimum, and overdose system) during storage was also studied. Oscillatoria sp. cells can be removed efficiently by coagulation of PAFC. The adverse environmental stresses of sludge, such as lack of light and anoxic environment, decrease cell viability and induce the increase of superoxide dismutase activity (SOD) and malondialdehyde content (MDA) in Oscillatoria sp. cells during the first 4 days. Because Oscillatoria sp. can adapt to the low-light and hypoxic circumstances in sludge gradually, the cells regrow with prolonged storage time. Compared to planktonic Microcystis aeruginosa and Cylindrospermopsis raciborskii , regrowth of Oscillatoria sp. during storage may present a bigger threat, even though Microcystis aeruginosa and Cylindrospermopsis raciborskii cells will be damaged and release toxic compounds. Growth rates of algae in coagulated systems were lower than that in control system because of the restriction of flocs. It is worth noting that the chlorophyll a level was increased by a factor of 3.5 in the optimal-dose system, and worse, the overdose system increased by a factor of 6 in chlorophyll a after 8 d storage due to the benefit of higher Fe levels. Concentrations of extracellular geosmin and cylindrospermopsin also increased during storage, especially after 4 d, and varied in the following sequence for a given storage duration: control system > overdose system > optimum system. Overall, due to decrease of SOD and MDA in Oscillatoria sp. cells after 4 d storage, algae cells regrew rapidly, especially in overdose system. Hence, sludge should be treated within 4 d and excess PAFC dosing should be avoided. [ABSTRACT FROM AUTHOR]

Cells trigger the assembly of stress granules (SGs) under various stress conditions. Among the many proteins recruited to SGs are RNA-binding proteins and transcription regulators. Here, we report the translocation of human (h)Cdc73, a component of the PAF1 transcription complex, to cytosolic SGs in response to arsenic stress. The hCdc73 protein possesses a long intrinsically disordered region (IDR) from amino acids 256-416, the presence of which is required for the translocation of hCdc73 to cytosolic SGs. The purified hCdc73 IDR formed droplets in vitro, and the light-activated assembly of hCdc73-IDR-mCherry-CRY2 was verified. For translocation of hCdc73 to SGs, physical interactions with SG carrier proteins, such as FMR1, are also needed. Previously, we reported that the cytosolic hCdc73-eEF1Bγ complex controls the stability of p53 mRNA. Under arsenic stress, selective sequestration of cytosolic hCdc73, but not eEF1Bγ (EEF1G) or p53 (TP53) mRNA, was detected. As a result, a transient increase in p53 mRNA at the post-transcriptional level was observed. In conclusion, we propose that the availability of mRNAs for stress-responsive genes can be controlled by restraining their negative regulators within SGs., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2023. Published by The Company of Biologists Ltd.)

• Fracture toughness of SIFCON specimen is higher than that PAFC. • Pure mode III exhibited the lowest effective fracture toughness. • Higher fibre dosage in SIFCON results in higher compressive strength. • The mixtures made of HSF had the highest fracture toughness in all loading modes. Concrete is the most widely used and inexpensive material in the construction sector. However, due to its weakness in tension, the cracking and brittle fracturing of concrete is considered a major deficiency. Advancements in fibrous concretes have recently been emerged to mitigate this issue. Preplaced Aggregate Fibrous Concrete (PAFC) and Slurry Infiltrated Fibrous Concrete (SIFCON) are unique cement composites made of fibres with surpassing mechanical properties and exceptional toughness values. The production of PAFC and SIFCON involves packing of aggregates and fibres in the mould and filling the gaps between the aggregates with the high flowability injected cement grout. Nevertheless, the mono and hybrid layered effect of PAFC and SIFCON on fracture toughness is still unexplored and needs special attention to bridge this research gap. This research examined the pure (I and III) and mixed (I/III) modes of fracture toughness of PAFC, SIFCON and hybrid two-layered PAFC-SIFCON samples. For this purpose, many notched specimens of circular disc shapes were prepared using single and double-layer concepts. To investigate the effect of fibres, three different fibre types were used; hooked-end steel fibre, macro polypropylene fibre and hybrid shape of crimped-hooked end steel fibre with dosages of 2.4% and 8% by volume to produce PAFC and SIFCON, respectively. Additionally, multi-walled nano-carbon tubes (MWCNT) were added to the composites with a dosage of 0.1% by cement weight. The compressive strength, stress intensity factors, effective stress intensity factors, mixity parameter, failure pattern, range of fracture toughness and scanning electron microscope were examined, discussed, and compared. Results indicated that pure mode III has a greater cracking risk than both mode I and mixed-mode I/III. The mixed-mode fracture toughness of PAFC specimens improved by 33.07 to 67.94%. Similarly, this improvement ranged from 59.77 to 210.70% for SIFCON and from 51.0 to 131.55% for PAFC-SIFCON. In addition, the fracture toughness of SIFCON is considerably higher than the PAFC and hybrid combination. In all three composite types, the hybrid shape steel fibre outperformed the hooked-end steel and polypropylene fibre under all three modes. [ABSTRACT FROM AUTHOR]

Fuel cell and electrolysis depend critically on catalysis. Haldor Topsøe has been a leader in this field and initiated many innovations. The paper reviews the types of fuel cells, electrolyzers, and the thermodynamic aspects involved, and then discusses the technology from the viewpoint of available feedstocks. Important phenomena that determine the stability of the devices, such as carbon deposition and sulfur poisoning, are reviewed as well. Although fuel cells are still awaiting their commercial breakthrough, high-temperature electrolysis in combination with the catalytic synthesis undoubtedly has potential in sustainable energy scenarios. [ABSTRACT FROM AUTHOR]

[Display omitted] • First study of membrane technology to remove impurities from stevia extract. • FeSO 4 forms complexes with organic compounds causing serious membrane fouling. • PAFC can remove impurities more effectively and reduce membrane fouling. • Hydrodynamic flux and trans-membrane current were used to quantify membrane fouling. Stevia sugar is widely used in food owing to its advantages of low calorie content and high sweetness. In the production of stevia sugar, stevia leaves are immersed in water to obtain a crude liquor, which contains many impurities, such as proteins, polysaccharides, organic acids, etc. These impurities are removed typically by coagulation and filtration. At present, suppliers of stevia mainly use a "lime + ferrous sulfate (FeSO 4)" process as the pretreatment, but residual SO 4 2− can cause hydrogen sulfide corrosion and Ca2+ can affect the safety of subsequent boilers in the process. In this study, polyaluminium ferric chloride (PAFC) was evaluated as a superior coagulant to FeSO 4 , together with ultrafiltration (UF) and nanofiltration to remove flocs and other organic contaminants. It was found that coagulation by PAFC out-performed FeSO 4 and was unaffected by pH, while the performance of FeSO 4 was sensitive to pH. At pH 10, FeSO 4 had an enhanced coagulation efficiency, but formed soluble Fe2+ complexes with organic substances in the original solution, which adversely affected the quality of the filtrate. Compared with a UF membrane, the NF membrane was more effective in removing contaminants, and more tolerant to membrane fouling. In addition to hydrodynamic flux, measurement of trans-membrane electrical current were used to reflect the severity of membrane fouling. The combination of PAFC as coagulant without pH adjustment, and ultrafiltration, was found to be a simpler and superior treatment for stevia liquor with a high degree of contaminant separation, and avoidance of problems caused by SO 4 2− and Ca2+. [ABSTRACT FROM AUTHOR]

Poly aluminum-ferric Chloride (PAFC) is a new type of high efficiency coagulant. In this study, high iron type gangue is used as a main raw material. It is calcined at 675 °C for 1 h and 3% CaF 2 is added to the calcined powder and reacted with 20% hydrochloric acid at 93 °C for 4 h. The leaching ratio of aluminum ions is 90% and that of iron ions is 91%. After Fe 2+ ions are oxidized in the filtrate, CaCO 3 is used to adjust the pH of the filtrate to 0.7. The microwave power is adjusted to 80 W and the filtrate is radiated for 5 min. After being aged for 24 h, PAFC product is obtained. The prepared PAFC is used to treat mine water and compared with the results of PAC and PAF, the turbidity removal ratio of PAFC is 99.6%, which is greater than 96.4% of PAC and 93.7% of PAF. PAFC is a mixture with different degrees of polymerization. It demonstrates that extracting aluminum and iron ions from high iron content gangue to prepare PAFC by microwave is efficient and feasible.

• PAFC is a better alternative coagulant of FeSO 4 in Stevia pretreatment. • PAFC has higher impurity removal and no residual Fe(Ⅱ)-complex. • Solution pH had little effect on the performance of PAFC, but great effect on FeSO 4. • The addition of CaO increased membrane flux of the two coagulants. • The interaction between organic matter and nanoparticles blocked the gap of cake layer. Stevioside, mainly extracted from Stevia rebaudiana, is an important non-caloric additive for food, beverages and flavoring, and an alternative natural sweetener for people with diabetes and obesity. Pretreatment of Stevia rebaudiana, involving coagulation and filtration, is used to remove impurities from the leach liquor of stevia. Commercially, ferrous sulfate (FeSO 4) is commonly used as a coagulant in the factory, but large amounts of soluble Fe(Ⅱ)-protein complexes remain in the filtrate, which is potentially of health concern. In this study, the removal of impurities (particles and organic compounds) in leach liquor of stevia by polymeric aluminium ferric chloride (PAFC) was compared to FeSO 4 , through simulated coagulation and membrane filtration processes. The results showed that PAFC has a superior coagulation efficiency to FeSO 4 , achieving a very high removal of the impurities in the leaching solution without complexation, and which was not affected by the solution pH. In the subsequent membrane filtration, the flux was found to be influenced (reduced) by the interaction between organic matter (e.g. proteins) and nanoparticles in the cake layer, which formed a dense and compact structure with a lower permeability. Although using FeSO 4 had a greater membrane flux, the results have shown significant advantages in using PAFC as an alternative coagulant to FeSO 4 in the pre-treatment of leach liquor from Stevia processing. The higher treatment performance and acceptable membrane flux could be obtained by adjusting the pH of the leaching solution to 7 (addition of CaO), at the optimal PAFC dose (5000 mg/L). [ABSTRACT FROM AUTHOR]

Aim: Mycobacterium tuberculosis possesses an intracellular tagging and degradation system, which has emerged as a target for development of anti-tuberculosis agents. In this system, PafA is the ligase that marks proteins for degradation by their covalent modification with a protein modifier. Here, we studied pafA transcriptional regulation, which remained elusive despite its importance for M. tuberculosis virulence., Materials & Methods: Working with Mycobacterium smegmatis, a mycobacterial model organism, we examined the involvement of the global regulators PafB and PafC in pafA regulation., Results: PafBC activated pafA transcription following DNA damage, resulting in efficient cellular recovery., Conclusion: The results unraveled the involvement of PafBC in pafA transcription, and revealed the importance of proper PafA regulation in mycobacterial physiology.

The human RNA polymerase II (RNAPII)-associated factor complex (hPAFc) and its individual subunits have been implicated in human diseases, including cancer. However, its involvement in breast cancer awaits investigation. Using data mining and human breast cancer tissue microarrays, we found that Ctr9, the key scaffold subunit in hPAFc, is highly expressed in estrogen receptor α-positive (ERα+) luminal breast cancer, and the high expression of Ctr9 correlates with poor prognosis. Knockdown of Ctr9 in ERα+ breast cancer cells almost completely erased estrogen-regulated transcriptional response. At the molecular level, Ctr9 enhances ERα protein stability, promotes recruitment of ERα and RNAPII, and stimulates transcription elongation and transcription-coupled histone modifications. Knockdown of Ctr9, but not other hPAFc subunits, alters the morphology, proliferative capacity, and tamoxifen sensitivity of ERα+ breast cancer cells. T ogether, our study reveals that Ctr9, a key subunit of hPAFc, is a central regulator of estrogen signaling that drives ERα+ breast tumorigenesis, rendering it a potential target for the treatment of ERα+ breast cancer. [ABSTRACT FROM AUTHOR]

The human RNA polymerase II (RNAPII)-associated factor complex (hPAFc) and its individual subunits have been implicated in human diseases, including cancer. However, its involvement in breast cancer awaits investigation. Using data mining and human breast cancer tissue microarrays, we found that Ctr9, the key scaffold subunit in hPAFc, is highly expressed in estrogen receptor α-positive (ERα(+)) luminal breast cancer, and the high expression of Ctr9 correlates with poor prognosis. Knockdown of Ctr9 in ERα(+) breast cancer cells almost completely erased estrogen-regulated transcriptional response. At the molecular level, Ctr9 enhances ERα protein stability, promotes recruitment of ERα and RNAPII, and stimulates transcription elongation and transcription-coupled histone modifications. Knockdown of Ctr9, but not other hPAFc subunits, alters the morphology, proliferative capacity, and tamoxifen sensitivity of ERα(+) breast cancer cells. Together, our study reveals that Ctr9, a key subunit of hPAFc, is a central regulator of estrogen signaling that drives ERα(+) breast tumorigenesis, rendering it a potential target for the treatment of ERα(+) breast cancer., (© 2015 Zeng and Xu; Published by Cold Spring Harbor Laboratory Press.)