Efficient repair of DNA double-strand breaks (DSBs) is of critical importance for cell survival. Although non-homologous end joining (NHEJ) is the most used DSBs repair pathway in the cells, how NHEJ factors are sequentially recruited to damaged chromatin remains unclear. Here, we identify a novel role for the zinc-finger protein ZNF281 in participating in the ordered recruitment of the NHEJ repair factor XRCC4 at damage sites. ZNF281 is recruited to DNA lesions within seconds after DNA damage through a mechanism dependent on its DNA binding domain and, at least in part, on poly-ADP ribose polymerase (PARP) activity. ZNF281 binds XRCC4 through its zinc-finger domain and facilitates its recruitment to damaged sites. Consequently, depletion of ZNF281 impairs the efficiency of the NHEJ repair pathway and decreases cell viability upon DNA damage. Survival analyses from datasets of commonly occurring human cancers show that higher levels of ZNF281 correlate with poor prognosis of patients treated with DNA-damaging therapies. Thus, our results define a late ZNF281-dependent regulatory step of NHEJ complex assembly at DNA lesions and suggest additional possibilities for cancer patients’ stratification and for the development of personalised therapeutic strategies.

NEAT1 (Nuclear Enriched Abundant Transcript 1) is a long non-coding RNA playing a critical role in both physiological and pathological settings by directly modulating a variety of biological events, including transcriptional regulation, RNA processing, and chromatin remodeling. Multiple evidence demonstrated that different transcription factors and signaling pathways modulate biological processes by tightly regulating NEAT1 expression. These regulatory mechanisms act at different levels, allowing cells to rapidly modulate NEAT1 expression and dynamically respond to sudden changes in cellular conditions. In this review, we summarize and discuss the transcriptional routes controlling NEAT1 expression, emphasizing recent evidence showing the pivotal role of NEAT1 in regulating important biological processes, such as cellular stress response, inflammation, and cell differentiation.

Defects in achieving a fully differentiated state and aberrant expression of genes and microRNAs (miRs) involved in differentiation are common to virtually all tumor types. Here, we demonstrate that the zinc finger transcription factor ZNF281/Zfp281 is down‐regulated during epithelial, muscle and granulocytic differentiation in vitro. The expression of this gene is absent in terminally differentiated human tissues, in contrast to the elevated expression in proliferating/differentiating ones. Analysis of the 3’UTR of ZNF281/Zfp281 revealed the presence of numerous previously undescribed miR binding sites that were proved to be functional for miR‐mediated post‐transcriptional regulation. Many of these miRs are involved in differentiation pathways of distinct cell lineages. Of interest, ZNF281/Zfp281 is able to inhibit muscle differentiation promoted by miR‐1, of which ZNF281/Zfp281 is a direct target. These data suggest that down‐regulation of ZNF281/Zfp281 during differentiation in various cell types may occur through specific miRs whose expression is tissue‐restricted. In addition, we found that in rhabdomyosarcoma and leiomyosarcoma tumors the expression of ZNF281/Zfp281 is significantly higher compared with normal counterparts. We extended our analysis to other human soft tissue sarcomas, in which the expression of ZNF281 is associated with a worse prognosis. In summary, we highlight here a new role of ZNF281/Zfp281 in counteracting muscle differentiation; its down‐regulation is at least in part mediated by miR‐1. The elevated expression of ZNF281/Zfp281 in soft tissue sarcomas warrants further analysis for its possible exploitation as a prognostic marker in this class of tumors.

The transcription factor ΔNp63 plays a pivotal role in maintaining the integrity of stratified epithelial tissues by regulating the expression of distinct target genes involved in lineage specification, cell stemness, cell proliferation and differentiation. Here, we identified the ABC transporter subfamily member ABCC1 as a novel ΔNp63 target gene. We found that in immortalized human keratinocytes and in squamous cell carcinoma (SCC) cells, ∆Np63 induces the expression of ABCC1 by physically occupying a p63-binding site (p63 BS) located in the first intron of the ABCC1 gene locus. In cutaneous SCC and during the activation of the keratinocyte differentiation program, ∆Np63 and ABCC1 levels are positively correlated raising the possibility that ABCC1 might be involved in the regulation of the proliferative/differentiative capabilities of squamous tissue. However, we did not find any gross alteration in the structure and morphology of the epidermis in humanized hABCC1 knock-out mice. Conversely, we found that the genetic ablation of ABCC1 led to a marked reduction in inflammation-mediated proliferation of keratinocytes, suggesting that ABCC1 might be involved in the regulation of keratinocyte proliferation upon inflammatory/proliferative signals. In line with these observations, we found a significant increase in ABCC1 expression in squamous cell carcinomas (SCCs), a tumor type characterized by keratinocyte hyper-proliferation and a pro-inflammatory tumor microenvironment. Collectively, these data uncover ABCC1 as an additional ∆Np63 target gene potentially involved in those skin diseases characterized by dysregulation of proliferation/differentiation balance.

Head and neck squamous cell carcinomas (HNSCCs) are characterized by recurrent genetic alterations, including the inactivation of the tumor suppressor TP53 gene and dysregulation of the TP63 gene. The TP63 gene encodes multiple isoforms, among which the N‐terminal truncated isoform ΔNp63 is fundamental for the integrity of stratified epithelial tissues. We previously demonstrated that ΔNp63 represses the expression of the lncRNA NEAT1. Here, we investigated the functional crosstalk between p53 and ΔNp63 in modulating NEAT1 expression following genotoxic stress. We found that upon genotoxic insults, p53 activation and the concomitant downregulation of ΔNp63 promote NEAT1 transcription. In p53‐proficient HNSCC cells, NEAT1 targeting leads to increased DNA damage, highlighting its potential role in maintaining genomic stability and facilitating efficient DNA repair. Importantly, we showed that histone deacetylase inhibitors (HDACis) upregulate NEAT1 expression independently of p53, and NEAT1 silencing enhances HDACis‐induced DNA damage. Overall, our findings establish NEAT1 as an early regulator of the DNA damage response in HNSCCs and suggest that combining NEAT1 targeting with HDAC inhibition may potentiate therapeutic efficacy, particularly in TP53 ‐mutant HNSCCs.