URI Regulates KAP1 Phosphorylation and Transcriptional Repression via PP2A Phosphatase in Prostate Cancer Cells

Human cytomegalovirus infection induces L1 expression through UL38-dependent mTOR-KAP1 pathway

Human cytomegalovirus (HCMV) and LINE-1 (L1) can co-inhabit a common host and closely interact with each other within a single cell. We have previously shown that HCMV exploits this opportunistic interaction by upregulating L1 expression that promotes its own productive life cycle by facilitating HCMV DNA replication. However, the mechanism by which HCMV increases L1 expression remains unknown. Here, we report that HCMV infection functionally inactivates KRAB-associated protein 1 (KAP1), a key epigenetic repressor of L1, through phosphorylation. HCMV infection of cells activates mTOR kinase that phosphorylates S824 residue of KAP1 and reduces its epigenetic repressive function, leading to increased chromatin accessibility of L1 promoter region. Treatment of potent mTOR inhibitor to the HCMV-infected cells was sufficient to reduce KAP1 phosphorylation and block L1 expression. Furthermore, cells infected with a mutant virus lacking UL38, an HCMV mTOR pathway activator, showed reduced KAP1 S824 phosphorylation and abolished L1 expression. Our results highlight the synergistic interaction between HCMV and L1 where HCMV UL38 serves as a primary viral regulator of L1 expression by upregulating the mTOR-KAP1 pathway.

Multifaceted role of TRIM28 in health and disease

The TRIM (tripartite motif) family, with TRIM28 as a key member, plays a vital role in regulating health and disease. TRIM28 contains various functional domains essential for transcriptional regulation, primarily through its interaction with KRAB-ZNF proteins, which influence chromatin remodeling and gene expression. Despite extensive research, the precise mechanisms by which TRIM28 impacts health and disease remain elusive. This review delves into TRIM28's multifaceted roles in maintaining health, contributing to a variety of diseases, and influencing cancer progression. In cancers, TRIM28 exhibits a dual nature, functioning as both a tumor promoter and suppressor depending on the cellular context and cancer type. The review also explores its critical involvement in processes such as DNA repair, cell cycle regulation, epithelial-to-mesenchymal transition, and the maintenance of stem cell properties. By uncovering TRIM28's complex roles across different cancers and other diseases, this review underscores its potential as a therapeutic target. The significance of TRIM28 as a versatile regulator opens the door to innovative therapeutic strategies, particularly in cancer treatment and the management of other diseases. Ongoing research into TRIM28 may yield key insights into disease progression and novel treatment options.

Navigating the Landscape of Intestinal Regeneration: A Spotlight on Quiescence Regulation and Fetal Reprogramming

Tissue-specific adult stem cells are pivotal in maintaining tissue homeostasis, especially in the rapidly renewing intestinal epithelium. At the heart of this process are leucine-rich repeat-containing G protein-coupled receptor 5-expressing crypt base columnar cells (CBCs) that differentiate into various intestinal epithelial cells. However, while these CBCs are vital for tissue turnover, they are vulnerable to cytotoxic agents. Recent advances indicate that alternative stem cell sources drive the epithelial regeneration post-injury. Techniques like lineage tracing and single-cell RNA sequencing, combined with in vitro organoid systems, highlight the remarkable cellular adaptability of the intestinal epithelium during repair. These regenerative responses are mediated by the reactivation of conserved stem cells, predominantly quiescent stem cells and revival stem cells. With focus on these cells, this review unpacks underlying mechanisms governing intestinal regeneration and explores their potential clinical applications.

TRIM28 in cancer and cancer therapy

TRIM28 (tripartite motif protein 28) was initially believed to be a transcription inhibitor that plays an important role in DNA damage repair (DDR) and in maintaining cancer cellular stemness. As research has continued to deepen, several studies have found that TRIM28 not only has ubiquitin E3 ligase activity to promote degradation of substrates, but also can promote SUMOylation of substrates. Although TRIM28 is highly expressed in various cancer tissues and has oncogenic effects, there are still a few studies indicating that TRIM28 has certain anticancer effects. Additionally, TRIM28 is subject to complex upstream regulation. In this review, we have elaborated on the structure and regulation of TRIM28. At the same time, highlighting the functional role of TRIM28 in tumor development and emphasizing its impact on cancer treatment provides a new direction for future clinical antitumor treatment.

Maf1 phosphorylation is regulated through the action of prefoldin-like Bud27 on PP4 phosphatase in Saccharomyces cerevisiae

Bud27 is a prefoldin-like protein that participates in transcriptional regulation mediated by the three RNA polymerases in Saccharomyces cerevisiae. Lack of Bud27 significantly affects RNA pol III transcription, although the involved mechanisms have not been characterized. Here, we show that Bud27 regulates the phosphorylation state of the RNA pol III transcriptional repressor, Maf1, influences its nuclear localization, and likely its activity. We demonstrate that Bud27 is associated with the Maf1 main phosphatase PP4 in vivo, and that this interaction is required for proper Maf1 dephosphorylation. Lack of Bud27 decreases the interaction among PP4 and Maf1, Maf1 dephosphorylation, and its nuclear entry. Our data uncover a new nuclear function of Bud27, identify PP4 as a novel Bud27 interactor and demonstrate the effect of this prefoldin-like protein on the posttranslational regulation of Maf1. Finally, our data reveal a broader effect of Bud27 on PP4 activity by influencing, at least, the phosphorylation of Rad53.

UBE2D3 facilitates NHEJ by orchestrating ATM signalling through multi-level control of RNF168

Maintenance of genome integrity requires tight control of DNA damage response (DDR) signalling and repair, with phosphorylation and ubiquitination representing key elements. How these events are coordinated to achieve productive DNA repair remains elusive. Here we identify the ubiquitin-conjugating enzyme UBE2D3 as a regulator of ATM kinase-induced DDR that promotes non-homologous end-joining (NHEJ) at telomeres. UBE2D3 contributes to DDR-induced chromatin ubiquitination and recruitment of the NHEJ-promoting factor 53BP1, both mediated by RNF168 upon ATM activation. Additionally, UBE2D3 promotes NHEJ by limiting RNF168 accumulation and facilitating ATM-mediated phosphorylation of KAP1-S824. Mechanistically, defective KAP1-S824 phosphorylation and telomeric NHEJ upon UBE2D3-deficiency are linked to RNF168 hyperaccumulation and aberrant PP2A phosphatase activity. Together, our results identify UBE2D3 as a multi-level regulator of NHEJ that orchestrates ATM and RNF168 activities. Moreover, they reveal a negative regulatory circuit in the DDR that is constrained by UBE2D3 and consists of RNF168- and phosphatase-mediated restriction of KAP1 phosphorylation.

State-of-the-art in transposable element modulation affected by drugs in malignant prostatic cancer cells

Over recent years, the investigation of transposable elements (TEs) has granted researchers a deeper comprehension of their characteristics and functions, particularly regarding their significance in the mechanisms contributing to cancer development. This manuscript focuses on prostate carcinoma cell lines and offers a comprehensive review intended to scrutinize the associations and interactions between TEs and genes, as well as their response to treatment using various chemical drugs, emphasizing their involvement in cancer progression. We assembled a compendium of articles retrieved from the PubMed database to construct networks demonstrating correlations with genes and pharmaceuticals. In doing so, we linked the transposition of certain TE types to the expression of specific transcripts directly implicated in carcinogenesis. Additionally, we underline that treatment employing different drugs revealed unique patterns of TE reactivation. Our hypothesis gathers the current understanding and guides research toward evidence-based investigations, emphasizing the association between antiviral drugs, chemotherapy, and the reduced expression of TEs in patients affected by prostate cancer.

DIP-MS: ultra-deep interaction proteomics for the deconvolution of protein complexes

Most proteins are organized in macromolecular assemblies, which represent key functional units regulating and catalyzing most cellular processes. Affinity purification of the protein of interest combined with liquid chromatography coupled to tandem mass spectrometry (AP-MS) represents the method of choice to identify interacting proteins. The composition of complex isoforms concurrently present in the AP sample can, however, not be resolved from a single AP-MS experiment but requires computational inference from multiple time- and resource-intensive reciprocal AP-MS experiments. Here we introduce deep interactome profiling by mass spectrometry (DIP-MS), which combines AP with blue-native-PAGE separation, data-independent acquisition with mass spectrometry and deep-learning-based signal processing to resolve complex isoforms sharing the same bait protein in a single experiment. We applied DIP-MS to probe the organization of the human prefoldin family of complexes, resolving distinct prefoldin holo- and subcomplex variants, complex-complex interactions and complex isoforms with new subunits that were experimentally validated. Our results demonstrate that DIP-MS can reveal proteome modularity at unprecedented depth and resolution.

URI alleviates tyrosine kinase inhibitors-induced ferroptosis by reprogramming lipid metabolism in p53 wild-type liver cancers

The clinical benefit of tyrosine kinase inhibitors (TKIs)-based systemic therapy for advanced hepatocellular carcinoma (HCC) is limited due to drug resistance. Here, we uncover that lipid metabolism reprogramming mediated by unconventional prefoldin RPB5 interactor (URI) endows HCC with resistance to TKIs-induced ferroptosis. Mechanistically, URI directly interacts with TRIM28 and promotes p53 ubiquitination and degradation in a TRIM28-MDM2 dependent manner. Importantly, p53 binds to the promoter of stearoyl-CoA desaturase 1 (SCD1) and represses its transcription. High expression of URI is correlated with high level of SCD1 and their synergetic expression predicts poor prognosis and TKIs resistance in HCC. The combination of SCD1 inhibitor aramchol and deuterated sorafenib derivative donafenib displays promising anti-tumor effects in p53-wild type HCC patient-derived organoids and xenografted tumors. This combination therapy has potential clinical benefits for the patients with advanced HCC who have wild-type p53 and high levels of URI/SCD1.

Macrophage Rmp Ameliorates Myocardial Infarction by Modulating Macrophage Polarization in Mice

Background

Inflammation plays important roles during myocardial infarction (MI). Macrophage polarization is a major factor that drives the inflammatory process. Our previous study found that RNA polymerase II subunit 5-mediating protein (RMP) knockout in cardiomyocytes caused heart failure by impairing mitochondrial structure and function. However, whether macrophage RMP plays a role in MI has not been investigated.

Methods

Macrophage RMP-knockout in combination with a mouse model of MI was used to study the function of macrophage RMP in MI. Next, we modified bone marrow-derived macrophages (BMDMs) by plasmid transfection, and the BMDMs were administered to LysM-Cre/DTR mice by tail vein injection. Immunoblotting and immunofluorescence were used to detect macrophage polarization, fibrosis, angiogenesis, and the p38 signaling pathway in each group.

Results

Macrophage RMP deficiency aggravates cardiac dysfunction, promotes M1 polarization, and inhibits angiogenesis after MI. However, RMP overexpression in macrophages promotes M2 polarization and angiogenesis after MI. Mechanistically, we found that RMP regulates macrophage polarization through the heat shock protein 90- (HSP90-) p38 signaling pathway.

Conclusions

Macrophage RMP plays a significant role in MI, likely by regulating macrophage polarization via the HSP90-p38 signaling pathway.

A comprehensive analysis of prefoldins and their implication in cancer

Prefoldins (PFDNs) are evolutionary conserved co-chaperones, initially discovered in archaea but universally present in eukaryotes. PFDNs are prevalently organized into hetero-hexameric complexes. Although they have been overlooked since their discovery and their functions remain elusive, several reports indicate they act as co-chaperones escorting misfolded or non-native proteins to group II chaperonins. Unlike the eukaryotic PFDNs which interact with cytoskeletal components, the archaeal PFDNs can bind and stabilize a wide range of substrates, possibly due to their great structural diversity. The discovery of the unconventional RPB5 interactor (URI) PFDN-like complex (UPC) suggests that PFDNs have versatile functions and are required for different cellular processes, including an important role in cancer. Here, we summarize their functions across different species. Moreover, a comprehensive analysis of PFDNs genomic alterations across cancer types by using large-scale cancer genomic data indicates that PFDNs are a new class of non-mutated proteins significantly overexpressed in some cancer types.

Structure, Activity and Function of the SETDB1 Protein Methyltransferase

The SET Domain Bifurcated Histone Lysine Methyltransferase 1 (SETDB1) is a prominent member of the Suppressor of Variegation 3–9 (SUV39)-related protein lysine methyltransferases (PKMTs), comprising three isoforms that differ in length and domain composition. SETDB1 is widely expressed in human tissues, methylating Histone 3 lysine 9 (H3K9) residues, promoting chromatin compaction and exerting negative regulation on gene expression. SETDB1 has a central role in normal physiology and nervous system development, having been implicated in the regulation of cell cycle progression, inactivation of the X chromosome, immune cells function, expression of retroelements and formation of promyelocytic leukemia (PML) nuclear bodies (NB). SETDB1 has been frequently deregulated in carcinogenesis, being implicated in the pathogenesis of gliomas, melanomas, as well as in lung, breast, gastrointestinal and ovarian tumors, where it mainly exerts an oncogenic role. Aberrant activity of SETDB1 has also been implicated in several neuropsychiatric, cardiovascular and gastrointestinal diseases, including schizophrenia, Huntington’s disease, congenital heart defects and inflammatory bowel disease. Herein, we provide an update on the unique structural and biochemical features of SETDB1 that contribute to its regulation, as well as its molecular and cellular impact in normal physiology and disease with potential therapeutic options.

URI1 suppresses irradiation-induced reactive oxygen species (ROS) by activating autophagy in hepatocellular carcinoma cells

Radiotherapy has been extensively applied in cancer treatment. However, this treatment is ineffective in Hepatocellular carcinoma (HCC) due to lack of radiosensitivity. Unconventional prefoldin RPB5 interactor 1 (URI1) exhibits characteristics similar to those oncoproteins, which promotes survival of cancer cells. As a consequence of the irradiation, the levels of endogenous reactive oxygen species (ROS) rise. In the current study, we analyzed the role of URI1 in the control of ROS levels in HepG2 cells. Upon URI1 overexpression, HepG2 cells significantly suppressed irradiation-induced ROS, which may help cells escape from oxidative toxicity. And our data demonstrated that overexpression of URI1 not only resulted in an increase of autophagic flux, but also resulted in an further increased capacity of autophagy to eliminate ROS. It indicated that URI1 suppressed irradiation-induced ROS through activating autophagy. Moreover, URI1 activated autophagy by promoting the activities of AMP-activated protein kinase (AMPK). Results showed that overexpression of URI1 increased the phosphorylation of AMPKα at the Thr172 residue and the activated-AMPK promoted the phosphorylation of forkhead box O3 (FOXO3) at the Ser253 residue, which significantly induced autophagy. Taken together, our findings provide a mechanism that URI1 suppresses irradiation-induced ROS by activating autophagy through AMPK/FOXO3 signaling pathway. These new molecular insights will provide an important contribution to our better understanding about irradiation insensitivity of HCC.

Histone Methyltransferase SETDB1: A Common Denominator of Tumorigenesis with Therapeutic Potential

Epigenetic regulation of gene expression has been ultimately linked to cancer development, with posttranslational histone modifications representing attractive targets for disease monitoring and therapy. Emerging data have demonstrated histone lysine (K) methylation by methyltransferase SETDB1 as a common denominator of gene regulation in several cancer types. SETDB1 reversibly catalyzes the di- and trimethylation of histone 3 (H3) K9 in euchromatic regions of chromosomes, inhibiting gene transcription within these regions and promoting a switch from euchromatic to heterochromatic states. Recent studies have implicated aberrant SETDB1 activity in the development of various types of cancers, including brain, head and neck, lung, breast, gastrointestinal, ovarian, endometrial and prostate cancer, mesothelioma, melanoma, leukemias, and osteosarcoma. Although its role has not been fully elucidated in every case, most data point toward a pro-oncogenic potential of SETDB1 via the downregulation of critical tumor-suppressive genes. Less commonly, however, SETDB1 can also acquire a tumor-suppressive role, depending on cancer type and stage. Here we provide an updated overview of the cellular and molecular effects underlying SETDB1 activity in cancer development and progression along with current targeting strategies in different cancer types, with promising effects either as a standalone therapy or in conjunction with other therapeutic agents.

RPB5-Mediating Protein Promotes Cholangiocarcinoma Tumorigenesis and Drug Resistance by Competing With NRF2 for KEAP1 Binding

BACKGROUND AND AIMS

Cancer cell survival depends on the balance between reactive oxygen species production and scavenging, which is regulated primarily by NRF2 during tumorigenesis. Here, we demonstrate that deletion of RBP5-mediating protein (RMP) in an autonomous mouse model of intrahepatic cholangiocarcinoma (ICC) delays tumor progression.

APPROACH AND RESULTS

RMP-overexpressing tumor cells exhibited enhanced tolerance to oxidative stress and apoptosis. Mechanistically, RMP competes with NRF2 for binding to the Kelch domain of KEAP1 (Kelch-like ECH-associated protein 1) through the E**E motif, leading to decreased NRF2 degradation via ubiquitination, thus increasing NRF2 nuclear translocation and downstream transactivation of antioxidant genes. This RMP-KEAP1-NRF2 axis promotes ICC tumorigenesis, metastasis, and drug resistance. Consistent with these findings, the RMP level in human ICC is positively correlated with the protein level of NRF2 and is associated with poor prognosis.

CONCLUSION

These findings reveal that RMP is involved in the oxidative stress defense program and could be exploited for targeted cancer therapies.

A re-evaluation of LINE-1 ORF2 expression in LNCaP prostate cancer cells

Background

We previously examined expression of Long Interspersed Element-1 (LINE-1) in a variety of prostate cancer cells including hormone-dependent LNCaP cells. These studies demonstrated expression and sub-cellular localization of LINE-1 proteins, ORF1p, with antibody 4H1, and ORF2p, with antibody chA1-L1.

Results

Here we conduct immunoprecipitation/mass spectrometry analysis using chA1-L1 antibody against ORF2p in LNCaP cells. Our results indicate that antigens detected by the antibody include the transcriptional regulator BCLAF1. We show that chA1-L1 recognizes BCLAF1 using siRNA knockdown and overexpression of a tagged BCLAF1. We also show that chA1-L1 antibody recognizes ORF2p in HEK293 cells overexpressing LINE-1. Further, analysis of ORF2p (chA1-L1) and BCLAF1 foci using immunofluorescence in LNCaP cells showed significant colocalization.

Conclusions

Overall, our findings indicate that chA1-L1 antibody recognizes both BCLAF1 and ORF2p but the majority of antigen recognized in LNCaP cells is BCLAF1.

Deletion of the SAPS1 subunit of protein phosphatase 6 in mice increases radiosensitivity and impairs the cellular DNA damage response

Cellular responses to DNA damage include activation of DNA-dependent protein kinase (DNA-PK) through, among others, the serine/threonine protein phosphatase 6 (PP6). We previously showed that recognition of DNA-PKcs is mediated by the SAPS1 PP6 regulatory subunit. Here, we report and characterize a SAPS1 null mouse and investigate the effects of deletion on DNA damage signaling and repair. Strikingly, neither SAPS1-null animals nor cells derived from them show gross defects, unless subjected to DNA damage by radiation or chemical agents. The overall survival of SAPS1-null animals following whole body irradiation is significantly shortened as compared to wild-type mice, and the clonogenic survival of null cells subjected to ionizing radiation is reduced. The dephosphorylation of DNA damage/repair markers, such as γH2AX, p53 and Kap1, is diminished in SAPS1-null cells as compared to wild-type controls. Our results demonstrate that loss of SAPS1 confers sensitivity to DNA damage and confirms previously reported cellular phenotypes of SAPS1 knock-down in human glioma cells. The results support a role for PP6 regulatory subunit SAPS1 in DNA damage responses, and offer a novel target for sensitization to enhance current tumor therapies, with a potential for limited deleterious side effects.

Prostate-specific loss of UXT promotes cancer progression

Ubiquitously-expressed, prefoldin-like chaperone (UXT) also called Androgen Receptor Trapped clone-27 (ART-27) is widely expressed in human tissues. Our previous studies showed that UXT regulates transcription repression including androgen receptor (AR) signaling in prostate cancer. Here we analyzed a tissue microarray consisting of normal prostate, benign prostatic hyperplasia, high grade prostatic intraepithelial neoplasia (HGPIN) and primary prostate cancer cases for UXT protein expression. We found that HGPIN and malignant tumors have significantly decreased UXT expression compared to the normal prostate. Loss of UXT expression in primary prostate cancer is positively associated with high Gleason grade and poor relapse-free survival. We engineered prostate-specific Uxt^KO mice that developed a hyperplastic phenotype with apparent prostate secretion fluid blockage as well as PIN by 4-6 months. Doubly mutant Uxt^KO/Pten^KO mice developed a more aggressive PIN phenotype. UXT depletion in prostate cancer cells also increased retroelements expression, including LINE-1 and Alu. Consistent with this finding Uxt^KO mice have increased LINE-1 protein levels in the prostate compared to control mice. In addition, cancer cells with UXT depletion have increased retrotransposition activity and accumulated DNA damage. Our findings demonstrate that loss of UXT is an early event during prostate cancer progression, which may contribute to genome instability.

The Expression of MicroRNA-598 Inhibits Ovarian Cancer Cell Proliferation and Metastasis by Targeting URI

Unconventional prefoldin RPB5 interactor (URI, or RMP, a member of the prefoldin family of molecular chaperones) exhibits oncogenic activity in several types of cancer, including ovarian cancer. However, the underlying regulatory mechanism in ovarian cancer remains unclear. MicroRNAs (miRNAs) negatively regulate gene expression, and their dysregulation has been implicated in tumorigenesis. To elucidate the role of miRNAs in URI-induced ovarian cancer, miR-598 and URI were overexpressed in the SKOV3 ovarian cancer cell line. The CCK8 kit was used to determine cell proliferation, and the Transwell assay was used to measure cell invasion and migration. RT-PCR and western blotting were used to analyze the expression of miR-598 and URI, and the luciferase reporter assay was used to examine the interaction between miR-598 and URI. Nude mice were used to characterize the regulation of tumor growth in vivo. The results showed that the expression of miR-598 inhibited the proliferation, invasion, and migration of ovarian cancer cells by targeting URI. The inhibitory effect of miR-598 was reversed by overexpression of URI. The luciferase reporter assay showed that miR-598 downregulated URI by directly targeting the 3′ UTR of URI. In vivo studies showed that the expression of miR-598 significantly inhibited the growth of tumors. Taken together, the results suggested that miR-598 inhibited tumor growth and metastasis by targeting URI.

Transcription factor profiling reveals molecular choreography and key regulators of human retrotransposon expression

Transposable elements (TEs) represent a substantial fraction of many eukaryotic genomes, and transcriptional regulation of these factors is important to determine TE activities in human cells. However, due to the repetitive nature of TEs, identifying transcription factor (TF)-binding sites from ChIP-sequencing (ChIP-seq) datasets is challenging. Current algorithms are focused on subtle differences between TE copies and thus bias the analysis to relatively old and inactive TEs. Here we describe an approach termed "MapRRCon" (mapping repeat reads to a consensus) which allows us to identify proteins binding to TE DNA sequences by mapping ChIP-seq reads to the TE consensus sequence after whole-genome alignment. Although this method does not assign binding sites to individual insertions in the genome, it provides a landscape of interacting TFs by capturing factors that bind to TEs under various conditions. We applied this method to screen TFs' interaction with L1 in human cells/tissues using ENCODE ChIP-seq datasets and identified 178 of the 512 TFs tested as bound to L1 in at least one biological condition with most of them (138) localized to the promoter. Among these L1-binding factors, we focused on Myc and CTCF, as they play important roles in cancer progression and 3D chromatin structure formation. Furthermore, we explored the transcriptomes of The Cancer Genome Atlas breast and ovarian tumor samples in which a consistent anti-/correlation between L1 and Myc/CTCF expression was observed, suggesting that these two factors may play roles in regulating L1 transcription during the development of such tumors.

Role of the Unconventional Prefoldin Proteins URI and UXT in Transcription Regulation

The Unconventional prefoldin RPB5 interacting protein (URI), also known as RPB5-Mediating Protein (RMP) has been shown to play several regulatory roles in different cellular compartments including the mitochondria, as a phosphatase binding protein; in the cytoplasm, as a chaperone-like protein; and in the nucleus, as a transcriptional regulator through binding to RPB5 and RNA polymerase II (polII). This chapter focuses on the role URI plays in transcriptional regulation in the prostate cell. In prostate cells, URI is tightly bound to another prefoldin-like protein called UXT, a known androgen receptor (AR) cofactor. Part of a multiprotein complex, URI and UXT act as transcriptional repressors, and URI regulates KAP1 through PP2A phosphatase activity. The discovery of the interaction of URI and UXT with KAP1, AR, and PP2A, as well as the numerous interactions between URI and components of the R2TP/prefoldin-like complex, RPB5, and nuclear proteins involved in DNA damage response, chromatin remodeling and gene transcription, reveal a pleiotropic effect of the URI/UXT complex on nuclear processes. The mechanisms by which URI/UXT affect transcription, chromatin structure and regulation, and genome stability, remain to be elucidated but will be of fundamental importance considering the many processes affected by alterations of URI/UXT and other prefoldins and prefoldin-like proteins.

Functional Contributions of Prefoldin to Gene Expression

Prefoldin is a co-chaperone that evolutionarily originates in archaea, is universally present in all eukaryotes and acts as a co-chaperone by facilitating the supply of unfolded or partially folded substrates to class II chaperonins. Eukaryotic prefoldin is known mainly for its functional relevance in the cytoplasmic folding of actin and tubulin monomers during cytoskeleton assembly. However, the role of prefoldin in chaperonin-mediated folding is not restricted to cytoskeleton components, but extends to both the assembly of other cytoplasmic complexes and the maintenance of functional proteins by avoiding protein aggregation and facilitating proteolytic degradation. Evolution has favoured the diversification of prefoldin subunits, and has allowed the so-called prefoldin-like complex, with specialised functions, to appear. Subunits of both canonical and prefoldin-like complexes have also been found in the nucleus of yeast and metazoan cells, where they have been functionally connected with different gene expression steps. Plant prefoldin has also been detected in the nucleus and is physically associated with a gene regulator. Here we summarise information available on the functional involvement of prefoldin in gene expression, and discuss the implications of these results for the relationship between prefoldin structure and function.

Role of the PAQosome in Regulating Arrangement of Protein Quaternary Structure in Health and Disease

The PAQosome, formerly known as the R2TP/PFDL complex, is an eleven-subunit cochaperone complex that assists HSP90 in the assembly of numerous large multisubunit protein complexes involved in essential cellular functions such as protein synthesis, ribosome biogenesis, transcription, splicing, and others. In this review, we discuss possible mechanisms of action and role of phosphorylation in the assembly of client complexes by the PAQosome as well as its potential role in cancer, ciliogenesis and ciliopathies.

The complexity of TRIM28 contribution to cancer

Since the first discovery in 1996, the engagement of TRIM28 in distinct aspects of cellular biology has been extensively studied resulting in identification of a complex nature of TRIM28 protein. In this review, we summarize core biological functions of TRIM28 that emerge from TRIM28 multi-domain structure and possessed enzymatic activities. Moreover, we will discuss whether the complexity of TRIM28 engagement in cancer biology makes TRIM28 a possible candidate for targeted anti-cancer therapy. Briefly, we will demonstrate the role of TRIM28 in regulation of target gene transcription, response to DNA damage, downregulation of p53 activity, stimulation of epithelial-to-mesenchymal transition, stemness sustainability, induction of autophagy and regulation of retrotransposition, to provide the answer whether TRIM28 functions as a stimulator or inhibitor of tumorigenesis. To date, number of studies demonstrate significant upregulation of TRIM28 expression in cancer tissues which correlates with worse overall patient survival, suggesting that TRIM28 supports cancer progression. Here, we present distinct aspects of TRIM28 involvement in regulation of cancer cell homeostasis which collectively imply pro-tumorigenic character of TRIM28. Thorough analyses are further needed to verify whether TRIM28 possess the potential to become a new anti-cancer target.