Biology subjects

Nagahama, M.

Publications and source records attributed to Nagahama, M..

3 recordsLinked to original sources

bioRxiv2025

Molecular basis of the autoregulatory mechanism of motor neuron-related splicing factor 30

Motor neuron-related splicing factor 30 (SPF30, also known as SMNDC1) is a paralog of the survival motor neuron protein that regulates the expression of various genes by affecting mRNA splicing. SPF30 has an autoregulatory mechanism that controls its expression. However, the detailed molecular mechanisms determining cellular levels of SPF30 remain unclear. Here, we demonstrated that SPF30 expression was controlled via the negative autoregulatory feedback, whereby increased SPF30 expression caused the inclusion of cassette exon within intron 2 and/or the generation of a newly spliced variant with exon 4a (produced by splicing 17 bp upstream of the canonical intron 3 and exon 4 junctions). Altered transcripts with cassette exon or exon 4a were subjected to nonsense-mediated mRNA decay, leading to reduced SPF30 mRNA levels. Conversely, the loss of SPF30 protein resulted in a drastic reduction in exon 4a inclusion compared to cassette exon inclusion, suggesting that exon 4a inclusion contributes more to adjusting SPF30 expression levels. An in vivo splicing assay designed to reflect exon 4a inclusion levels demonstrated that a short stretch of sequence within exon 4 of SPF30 mRNA was required for exon 4a inclusion. Additionally, the C-terminal region of SPF30 was crucial for the autoregulatory mechanism. Specifically, the C-terminal region of SPF30, including the latter part of -helix and a kink-like structure, was required for binding to RNA containing exon 4a. Collectively, these results reveal the molecular basis of the autoregulatory mechanism underlying SPF30 gene expression.

molecular biology↗

bioRxiv2021

The unique Brucella effectors NyxA and NyxB target SENP3 to modulate the subcellular localisation of nucleolar proteins

The cell nucleus is a primary target for intracellular bacterial pathogens to counteract immune responses and hijack host signalling pathways to cause disease. The mechanisms controlling nuclear protein localisation in the context of stress responses induced upon bacterial infection are still poorly understood. Here we show that the Brucella abortus effectors NyxA and NyxB interfere with the host sentrin specific protease 3 (SENP3), which is essential for intracellular replication. Translocated Nyx effectors directly interact with SENP3 via a defined acidic patch identified from the crystal structure of NyxB, preventing its nucleolar localisation at the late stages of the infection. By sequestering SENP3, the Nyx effectors induce the cytoplasmic accumulation of the nucleolar AAA-ATPase NVL, the large subunit ribosomal protein L5 (RPL5) and the ribophagy receptor NUFIP1 in Nyx-enriched structures in the vicinity of replicating bacteria. This shuttling of ribosomal biogenesis-associated nucleolar proteins is negatively regulated by SENP3 and dependent on the autophagy-initiation protein Beclin1, indicative of a ribophagy-derived process induced during Brucella infection. Our results highlight a new nucleomodulatory function by two unique Brucella effectors, and reveal that SENP3 is a critical regulator of the subcellular localisation of multiple nucleolar proteins during Brucella infection, promoting intracellular replication.

microbiology↗

bioRxiv2018

Identification of Functional Targets Reveals that the Suppression of Pumilio mediated mRNA Decay Increases Cell Resistance to DNA Damage in Human Cells

RNA-binding proteins (RBPs) play a pivotal role in gene expression by modulating the stability of transcripts; however, the identification of degradation targets of RBPs remains difficult. Here, we identified 48 target mRNAs of human Pumilio 1 (PUM1), an evolutionally conserved RBP, by combined analysis of transcriptome-wide mRNA stabilities and the binding of mRNAs to PUM1. Here, we developed an approach to identify mRNA targets of Pumilio 1 (PUM1), an evolutionally conserved RBP. By combined analysis of transcriptome-wide mRNA stabilities and the binding of mRNAs to PUM1, we identified 48 mRNAs that both bound to PUM1 and exhibited PUM1-dependent degradation. Analysis of changes in the abundance of PUM1 and its targets in RNA-seq data indicated that DNA-damaging agents negatively regulated PUM1-mediated mRNA decay. Cells exposed to cisplatin had reduced PUM1 abundance and increased PCNA and UBE2A mRNAs, encoding proteins involved in DNA repair by translesion synthesis (TLS). Cells overexpressing PUM1 exhibited impaired DNA synthesis and TLS and increased sensitivity to the cytotoxic effect of cisplatin. Thus, our method identified targets of PUM1-mediated decay and revealed that cells respond to DNA damage by inhibiting PUM1-mediated mRNA decay to activate TLS.

molecular biology↗