ALC1/eIF4A1-mediated regulation of CtIP mRNA stability controls DNA end resection

Effect and mechanism of the miR-1284/EIF4A1 axis on the cGAS-STING pathway under radiotherapy

Background

Gastric cancer (GC) remains a major global health concern, with limited treatment options, especially in advanced stages. Radiotherapy (RT) plays a vital role in GC management, but resistance to DNA damage impedes its effectiveness. MicroRNA-1284 (miR-1284), a tumor suppressor, regulates eukaryotic translation initiation factor 4A1 (EIF4A1), which is involved in DNA damage repair through homologous recombination (HR). This axis has been implicated in enhancing GC cell survival following RT. Additionally, the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway, activated by DNA damage, plays a key role in triggering an anti-tumor immune response. However, the interaction between the miR-1284/EIF4A1 axis, DNA repair, and the cGAS-STING pathway in GC under RT conditions remains unclear. This study aims to investigate how the miR-1284/EIF4A1 axis influences DNA repair and its role in activating the cGAS-STING pathway to enhance RT efficacy in GC.

Methods

A stably expressed messenger miR-1284 cell line was established. Quantitative reverse transcription and western blot were used to examine the expression of miR-1284 and EIF4A1, and the effect of blocking the miR-1284/EIF4A1 axis on the cGAS-STING pathway and interferon-β (IFN-β) in GC cells after RT; cytotoxicity experiments were conducted to explore the mechanism of the miR-1284/EIF4A1 axis in radiation-induced DNA damage repair; animal experiments were conducted to explore the translational application of rocaglamide (RocA) combined with the programmed cell death-ligand 1 (PD-L1) antibody in RT.

Results

The miR-1284/EIF4A1 axis in the GC cells promoted the repair of radiation-induced DNA damage and was associated with the prognosis of GC patients. Blocking this axis delayed the C-terminal binding protein interacting protein (CtIP)-mediated DNA repair, enhanced RT effectiveness, and activated the cGAS-STING pathway, while increasing the rate of apoptosis. In vivo experiments based on RocA binding to PD-L1 antibodies under RT had good biological safety, and thus provide a potential therapeutic strategy for the treatment of GC.

Conclusions

The miR-1284/EIF4A1 axis promotes the repair of DNA damage caused by RT, promotes the activation of the cGAS-STING pathway in GC, and has good biological safety. Our findings provide an important experimental basis for enhancing the anti-tumor immune effect of RT in the treatment of GC.

Cancer-associated transcription factors in DNA damage response

Transcription factors (TFs) constitute a wide and highly diverse group of proteins capable of controlling gene expression. Their roles in oncogenesis, tumor progression, and metastasis have been established, but recently their role in the DNA damage response pathway (DDR) has emerged. Many of them can affect elements of canonical DDR pathways, modulating their activity and deciding on the effectiveness of DNA repair. In this review, we focus on the latest reports on the effects of two TFs with dual roles in oncogenesis and metastasis (hypoxia-inducible factor-1 α (HIF1α), proto-oncogene MYC) and three epithelial-mesenchymal transition (EMT) TFs (twist-related protein 1 (TWIST), zinc-finger E-box binding homeobox 1 (ZEB1), and zinc finger protein 281 (ZNF281)) associated with control of canonical DDR pathways.

Recurrent chromosome reshuffling and the evolution of neo-sex chromosomes in parrots

The karyotype of most birds has remained considerably stable during more than 100 million years' evolution, except for some groups, such as parrots. The evolutionary processes and underlying genetic mechanism of chromosomal rearrangements in parrots, however, are poorly understood. Here, using chromosome-level assemblies of four parrot genomes, we uncover frequent chromosome fusions and fissions, with most of them occurring independently among lineages. The increased activities of chromosomal rearrangements in parrots are likely associated with parrot-specific loss of two genes, ALC1 and PARP3, that have known functions in the repair of double-strand breaks and maintenance of genome stability. We further find that the fusion of the ZW sex chromosomes and chromosome 11 has created a pair of neo-sex chromosomes in the ancestor of parrots, and the chromosome 25 has been further added to the sex chromosomes in monk parakeet. Together, the combination of our genomic and cytogenetic analyses characterizes the complex evolutionary history of chromosomal rearrangements and sex chromosomes in parrots.

Multiple roles for PARP1 in ALC1-dependent nucleosome remodeling

The SNF2 family ATPase Amplified in Liver Cancer 1 (ALC1) is the only chromatin remodeling enzyme with a poly(ADP-ribose) (PAR) binding macrodomain. ALC1 functions together with poly(ADP-ribose) polymerase PARP1 to remodel nucleosomes. Activation of ALC1 cryptic ATPase activity and the subsequent nucleosome remodeling requires binding of its macrodomain to PAR chains synthesized by PARP1 and NAD⁺ A key question is whether PARP1 has a role(s) in ALC1-dependent nucleosome remodeling beyond simply synthesizing the PAR chains needed to activate the ALC1 ATPase. Here, we identify PARP1 separation-of-function mutants that activate ALC1 ATPase but do not support nucleosome remodeling by ALC1. Investigation of these mutants has revealed multiple functions for PARP1 in ALC1-dependent nucleosome remodeling and provides insights into its multifaceted role in chromatin remodeling.

MRGBP, a member of the NuA4 complex, inhibits DNA double-strand break repair

The repair of DNA breaks takes place in the context of chromatin and thus involves the activity of chromatin remodelers. The nucleosome acetyltransferase of H4 (NuA4) remodeler complex enables DNA break repair by relaxing flanking chromatin. Here, we show that MRG domain binding protein (MRGBP), a member of this complex, acts as a general inhibitor of DNA double‐strand break repair. Upon its downregulation, repair is generally increased. This is particularly evident for the stimulation of early events of homologous recombination. Thus, MRGBP has an opposing role to the main catalytic subunits of the NuA4 complex. Our data suggest that MRGBP acts by limiting the activity of this complex in DNA repair, specifically by narrowing the extent of DNA‐end resection.

USP15 Enhances Re-epithelialization Through Deubiquitinating EIF4A1 During Cutaneous Wound Repair

Re-epithelialization is a fundamental process in wound healing that involves various cytokines and cells during cutaneous barrier reconstruction. Ubiquitin-specific peptidase 15 (USP15), an important member of the deubiquitinating enzymes (DUBs), removes ubiquitin chains from target proteins and maintains protein stability. However, the dynamic role of USP15 in epithelialization remains unclear. We aimed to investigate the regulatory function of USP15 in re-epithelialization. An excisional wound splinting model was established to evaluate the re-epithelialization rate in Usp15 knockout (KO) mice. Coimmunoprecipitation (Co-IP) and mass spectrum analyses were performed to identify USP15-interacting proteins. RNA-sequencing was performed for transcriptome analysis in keratinocytes and uploaded into NODE database (http://www.biosino.org/node, accession numbers: OEP000770 and OEP000763). First, a significant delay in epithelialization was observed in the Usp15 KO mice. Moreover, inhibition of cell migration and proliferation was observed in the USP15-silenced keratinocytes (HaCaTs). Moreover, we revealed for the first time that USP15 could interact with eukaryotic initiation factor 4A-1 (EIF4A1), thereby promoting translational efficacy in keratinocytes, which is essential for keratinocyte proliferation and migration. Conclusively, the USP15-EIF4A1 complex significantly accelerated re-epithelialization in wound healing. These observations helped elucidate the function and mechanisms of USP15 in modulating re-epithelialization in wound healing, providing a promising target for refractory wound treatment.