5-Methylcytosine (m5C) is one of the most prevalent internal modifications of messenger RNA (mRNA) in higher eukaryotes. Here we report that Y box protein 2 (YBX2) serves as a novel mammalian m5C binding protein to undergo liquid-liquid phase separation (LLPS) both in vivo and in vitro, and this YBX2-dependent LLPS is enhanced by m5C marked RNA. Furthermore, the crystal structure assay revealed that W100, as a distinct m5C binding site of YBX2, is critical in mediating YBX2 phase separation. Our study resolved the relationship between RNA m5C and phase separation, providing a clue for a new regulatory layer of epigenetics.

RNA-binding proteins (RBPs) fine-tune gene expression by modulating RNA stability, translation, and degradation. RBPs are involved in the development of endometrial cancer. In particular, Y-box-binding protein 2 (YBX2), a germ cell-specific member of the YBX family, has been reported to maintain cancer stem cell-like phenotypes in endometrial cancer. However, the mechanism by which YBX2 modulates mRNA stability in endometrial cancer cells remains unknown. In this study, we examined the effects of the ectopic expression of YBX2 in endometrial adenocarcinoma-derived Ishikawa cells. We found that elevated levels of YBX2 delayed cell proliferation, without increasing cell apoptosis. Transcriptomic analysis revealed disturbances in gene expression caused by YBX2. Interestingly, heat shock protein family A (Hsp70) member 6 (HSPA6) levels were downregulated due to the reduced mRNA stability after YBX2 binding. YBX2 facilitated the formation of relatively stable cytoplasmic granules in tumor cells via its mRNA binding domain. Moreover, N6-methyladenosine (m6A) reader proteins are recruited by YBX2 granules via the cold-shock domain. Notably, knockdown of YTH N6-methyladenosine RNA-binding protein F2 (YTHDF2), an m6A reader, ameliorated the reduction in HSPA6 mRNA levels induced by YBX2, indicating the synergistic effects of YBX2 and YTHDF2 on mRNA stability. Therefore, YBX2 regulates RNA stability by interacting with the m6A reader proteins.

Although 5-methylcytosine (m5C) has been identified as a novel and abundant mRNA modification and associated with energy metabolism, its regulation function in adipose tissue and skeletal muscle is still limited. This study aimed at investigating the effect of mRNA m5C on adipogenesis and myogenesis using Jinhua pigs (J), Yorkshire pigs (Y) and their hybrids Yorkshire-Jinhua pigs (YJ). We found that Y grow faster than J and YJ, while fatness-related characteristics observed in Y were lower than those of J and YJ. Besides, total mRNA m5C levels and expression rates of NSUN2 were higher both in backfat layer (BL) and longissimus dorsi muscle (LDM) of Y compared to J and YJ, suggesting that higher mRNA m5C levels positively correlate with lower fat and higher muscle mass. RNA bisulfite sequencing profiling of m5C revealed tissue-specific and dynamic features in pigs. Functionally, hyper-methylated m5C-containing genes were enriched in pathways linked to impaired adipogenesis and enhanced myogenesis. In in vitro, m5C inhibited lipid accumulation and promoted myogenic differentiation. Furthermore, YBX2 and SMO were identified as m5C targets. Mechanistically, YBX2 and SMO mRNAs with m5C modification were recognized and exported into the cytoplasm from the nucleus by ALYREF, thus leading to increased YBX2 and SMO protein expression and thereby inhibiting adipogenesis and promoting myogenesis, respectively. Our work uncovered the critical role of mRNA m5C in regulating adipogenesis and myogenesis via ALYREF-m5C-YBX2 and ALYREF-m5C-SMO manners, providing a potential therapeutic target in the prevention and treatment of obesity, skeletal muscle dysfunction and metabolic disorder diseases.

BNC1 is a transcription factor that is crucial for spermatogenesis and male fertility, although the underlying mechanism remains unclear. To study BNC1\'s specific role in spermatogenesis, we characterized a previously developed mouse model carrying a truncating mutation in Bnc1 (termed Bnc1+/tr for heterozygotes and Bnc1tr/tr for homozygotes) and found that the mutation decreased BNC1 protein levels and resulted in germ cell loss by apoptosis. Given that loss of functional Bnc1 is known to result in decreased expression of the spermatogenesis genes Ybx2 and Papolb, we aimed to explore whether and how BNC1 promotes transcription of Ybx2 and Papolb to mediate its role in spermatogenesis. We confirmed significant reduction in YBX2 and PAPOLB protein levels in testis tissue from Bnc1+/tr and Bnc1tr/tr males compared with wild-type mice (Bnc1+/+). Consistently, knockdown of Bnc1 led to downregulation of Ybx2 and Papolb in CRL-2196 cells in vitro. To investigate if BNC1 directly induces Ybx2 and Papolb gene expression, chromatin immunoprecipitation using mouse testicular tissue and luciferase reporter assays in HEK293 cells were used to identify functional binding of BNC1 to the Ybx2 and Papolb promoters at defined BNC1 binding sites. Taken together, this study reveals a mechanism for BNC1\'s role in spermatogenesis by directly binding to BNC1 binding elements in the promoter regions of both Ybx2 and Papolb and inducing transcription of these important spermatogenesis genes.

BACKGROUND: Oral squamous cell carcinoma (OSCC) is a type of oral malignancy. Long non-coding RNAs (lncRNAs) have been shown to be related to the occurrence and development of many cancers. Here, we aimed to study the role and molecular mechanism of lncRNA Homeobox A11 antisense RNA (HOXA11-AS) in OSCC.
METHODS: The expression levels of HOXA11-AS, miR-98-5p and Y box binding protein 2 (YBX2) were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Cell counting kit-8 (CCK-8), flow cytometry and transwell assays were utilized to determine the proliferation, apoptosis, migration and invasion of OSCC cells. Western blot (WB) analysis was conducted to measure the levels of apoptosis, epithelial-mesenchymal transition (EMT), proliferation-related proteins and YBX2 protein. Besides, Dual-luciferase reporter, RNA immunoprecipitation (RIP) and RNA pull down assays were carried out to examine the relationship among HOXA11-AS, miR-98-5p and YBX2. The mice xenograft models were constructed to further determine the effect of HOXA11-AS on OSCC tumor growth in vivo.
RESULTS: HOXA11-AS was highly expressed in OSCC tissues and cells. Knockdown of HOXA11-AS significantly reduced proliferation, migration, invasion and EMT, while promoted apoptosis of OSCC cells. MiR-98-5p was a target of HOXA11-AS, and its inhibitor could revert the inhibition effect of silenced-HOXA11-AS on the progression of OSCC. Also, YBX2 was a target of miR-98-5p, and its overexpression could invert the suppression effect of miR-98-5p overexpression on the progression of OSCC. YBX2 expression was regulated by HOXA11-AS and miR-98-5p. Furthermore, HOXA11-AS silencing could reduce the tumor growth of OSCC in vivo.
CONCLUSIONS: HOXA11-AS plays an active role in the progression of OSCC, and the discovery of HOXA11-AS/miR-98-5p/YBX2 axis provides new therapeutic targets for OSCC.

Oral squamous cell carcinoma (OSCC), the subtype of head and neck cancers, is notorious for its high incidence and death rate. The role of long non-coding RNAs (lncRNAs) is discovered to be significant for the canceration and cancer progression. Long intergenic non-protein coding RNA 958 (LINC00958) is discovered as a carcinogene in multiple cancers, such as gastric cancer, pancreatic cancer, and glioma, but there has been no report about how LINC00958 functions in OSCC. The objective of our study is to unfold function and mechanism investigation on LINC00958 in OSCC. First, TCGA database showed the upregulation and prognostic significance of LINC00958 in head and neck squamous carcinoma. Then, we discovered in OSCC clinical samples that LINC00958 presented high expression and predicted poor prognosis. Also, LINC00958 was elevated in OSCC cells. In vitro gain- and loss-function experiments proved that LINC00958 facilitated cell growth, retarded apoptosis, accelerated migration, and epithelial-to-mesenchymal transition (EMT) in OSCC. Mechanistically, we confirmed the cytoplasmic expression of LINC00958 in OSCC cells, and revealed that LINC00958 sequestered miR-627-5p to upregulate YBX2 expression. Rescue assays indicated that LINC00958 regulated OSCC cell proliferation, motility and EMT through YBX2. Together, we showed that LINC00958 promoted OSCC progression through miR-627-5p/YBX2 axis, indicating LINC00958 as a new prognostic marker, and provided new perspectives for molecular targeted treatment for OSCC.

The expression of many genes during the postmeiotic stages of spermatogenesis is largely regulated by germ cell-specific RNA-binding proteins at the level of posttranscription. One of these RNA-binding proteins, YBX2, participates in mRNA storage and regulation of translation in haploid spermatids. How YBX2-stored mRNAs become translationally competent during spermiogenesis remains unknown. In the present study, we report for the first time that YBX2 interacts with PAIP1, a protein translation enhancer, in vitro and in vivo. In murine testes, PAIP1 is highly expressed and colocalizes with YBX2 in round spermatids. Using sequential RNA immunoprecipitation and sequence analysis, we identified a group of spermiogenic mRNAs indirectly bound by PAIP1 through YBX2. Translation of mRNAs bearing the YBX2 target sequence was significantly blocked by YBX2 protein, but was reinitiated when YBX2 was coexpressed with PAIP1 in vitro. Taken together, these results indicate that PAIP1 regulates the translation of YBX2-masked mRNAs during spermiogenesis, and we propose this YBX2-PAIP1 interaction plays an important role in male germ cell development.