Genome-wide identification and expression analyses of Sm genes reveal their involvement in early somatic embryogenesis in Dimocarpus longan Lour

Genome-Wide Identification and Expression Analysis Reveal bZIP Transcription Factors Mediated Hormones That Functions during Early Somatic Embryogenesis in Dimocarpus longan

The basic leucine zip (bZIP) transcription factors (TFs) are a group of highly conserved gene families that play important roles in plant growth and resistance to adversity stress. However, studies on hormonal regulatory pathways and functional analysis during somatic embryogenesis (SE) in Dimocarpus longan is still unavailable. In this study, a total of 51 bZIP family members were systematically identified in the whole genome of longan, a comprehensive bioinformatics analysis of DlbZIP (bZIP family members of D. longan) was performed, and subcellular localization and profiles patterns after transiently transformed DlbZIP60 were analyzed. The combined analysis of RNA-seq, ATAC-seq and ChIP-seq showed that four members have different H3K4me1 binding peaks in early SE and differentially expressed with increased chromatin accessibility. Comparative transcriptome analysis of bZIPs expression in early SE, different tissues and under 2,4-D treatment revealed that DlbZIP family might involved in growth and development during longan early SE. The qRT-PCR results implied that DlbZIP family were subjected to multiple hormonal responses and showed different degrees of up-regulated expression under indole-3-acetic acid (IAA), abscisic acid (ABA) and methyl jasmonate (MeJA) treatments, which indicated that they played an important role in the hormone synthesis pathways associated with the early SE of longan. Subcellular localization showed that DlbZIP60 was located in the nucleus, and the contents of endogenous IAA, MeJA and ABA were up-regulated in transiently DlbZIP60 overexpressed cell lines. These results suggest that DlbZIP60 may mediate hormones pathways that functions the development during early SE in longan.

The splicing factor SNRPB promotes ovarian cancer progression through regulating aberrant exon skipping of POLA1 and BRCA2

Splicing factors play a crucial role in the initiation and development of various human cancers. SNRPB, a core spliceosome component, regulates pre-mRNA alternative splicing. However, its function and underlying mechanism in ovarian cancer remain unclear. This study identified SNRPB as a critical driver of ovarian cancer through TCGA and CPTAC database analysis. SNRPB was highly upregulated in fresh frozen ovarian cancer tissues compared with normal fallopian tubes. Immunohistochemistry revealed that SNRPB expression was increased in formalin-fixed, paraffin-embedded ovarian cancer sections and was positively correlated with a poor prognosis for ovarian cancer. Functionally, SNRPB knockdown suppressed ovarian cancer cell proliferation and invasion, and overexpression exerted opposite effects. SNRPB expression increased after cisplatin treatment, and silencing SNRPB sensitized ovarian cancer cells to cisplatin. KEGG pathway analysis revealed that the differentially expressed genes (DEGs) were mainly enriched in DNA replication and homologous recombination, and almost all DEGs related to DNA replication and homologous recombination were downregulated after SNRPB knockdown according to RNA-seq. Exon 3 skipping of the DEGs DNA polymerase alpha 1 (POLA1) and BRCA2 was induced by SNRPB silencing. Exon 3 skipping of POLA1 yielded premature termination codons and led to nonsense-mediated RNA decay (NMD); exon 3 skipping of BRCA2 led to loss of the PALB2 binding domain, which is necessary for homologous recombination, and increased ovarian cancer cell cisplatin sensitivity. POLA1 or BRCA2 knockdown partially impaired the increased malignancy of SNRPB-overexpressing ovarian cancer cells. Moreover, miR-654-5p was found to reduce SNRPB mRNA expression by directly binding to the SNRPB 3'-UTR. Overall, SNRPB was identified as an important oncogenic driver that promotes ovarian cancer progression by repressing exon 3 skipping of POLA1 and BRCA2. Thus, SNRPB is a potential treatment target and prognostic marker for ovarian cancer.

The Sm core components of small nuclear ribonucleoproteins promote homologous recombination repair

DNA Double strand breaks (DSBs) are highly hazardous to the cell, and are repaired predominantly via non-homologous end joining (NHEJ) and homologous recombination (HR). Using DSB-mimicking DNA templates, our proteomic studies identified a group of Sm core proteins of small nuclear ribonucleoproteins (snRNPs) as potential DSB-associated proteins. We further confirmed that these Sm proteins were recruited to laser-induced DNA damage sites, and co-localized with established DNA damage repair factors. Depletion of Sm-D3 or Sm-B induced accumulation of γ-H2AX, and impaired the repair efficiency of HR, but not NHEJ. Furthermore, disruption of Sm-D3 reduced the protein level of HR factors, especially RAD51 and CHK1, but caused no change in the expression of repair factors involved in NHEJ. Mechanistically, Sm-D3 proteins bound RAD51, suppressed the ubiquitination of RAD51, and mediated the stabilization of RAD51; Sm-D3 depletion particularly impacted the level of RAD51 and CHK1 on damaged chromatin. As such, our studies characterized a role of Sm proteins in HR repair, via a new mechanism that is distinct from their conventional functions in RNA processing and gene regulation, but consistent with their direct recruitment to DNA damage sites and association with repair factors.

Protein Arginine Methyltransferase 5 Functions via Interacting Proteins

The protein arginine methyltransferases (PRMTs) are involved in such biological processes as transcription regulation, DNA repair, RNA splicing, and signal transduction, etc. In this study, we mainly focused on PRMT5, a member of the type II PRMTs, which functions mainly alongside other interacting proteins. PRMT5 has been shown to be overexpressed in a wide variety of cancers and other diseases, and is involved in the regulation of Epstein-Barr virus infection, viral carcinogenesis, spliceosome, hepatitis B, cell cycles, and various signaling pathways. We analyzed the regulatory roles of PRMT5 and interacting proteins in various biological processes above-mentioned, to elucidate for the first time the interaction between PRMT5 and its interacting proteins. This systemic analysis will enrich the biological theory and contribute to the development of novel therapies.