Caiying Jiang

MicroRNA-452 promotes tumorigenesis in hepatocellular carcinoma by targeting cyclin-dependent kinase inhibitor 1B

Dysregulation of miR-452 has been observed in many tumors, but its biological function in hepatocellular carcinoma (HCC) is still unknown. Our results showed that miR-452 expression is significantly increased in HCC tissues and HCC cell lines. We also found that overexpression of miR-452 dramatically accelerated proliferation, induced cell cycle from G1 to S transition, and blocked apoptosis of HCC cells. Migration and matrigel invasion assays indicated that miR-452 significantly promotes HepG2 and QGY-7703 cells migration and invasion in vitro. Further studies showed that miR-452 directly targets the 3′-untranslated region of cyclin-dependent kinase inhibitor 1B (CDKN1B), ectopic miR-452 expression suppressed CDKN1B expression on mRNA and protein level. Silencing CDKN1B by small interfering RNA resembled the phenotype resulting from ectopic miR-452 expression. This study provides new insights into the potential molecular mechanisms that miRNA-452 contributed to HCC.

Comprehensive profiling of lysine acetylation suggests the widespread function is regulated by protein acetylation in the silkworm, Bombyx mori

Lysine acetylation in proteins is a dynamic and reversible PTM and plays an important role in diverse cellular processes. In this study, using lysine‐acetylation (Kac) peptide enrichment coupled with nano HPLC/MS/MS, we initially identified the acetylome in the silkworms. Overall, a total of 342 acetylated proteins with 667 Kac sites were identified in silkworm. Sequence motifs analysis around Kac sites revealed an enrichment of Y, F, and H in the +1 position, and F was also enriched in the +2 and –2 positions, indicating the presences of preferred amino acids around Kac sites in the silkworm. Functional analysis showed the acetylated proteins were primarily involved in some specific biological processes. Furthermore, lots of nutrient‐storage proteins, such as apolipophorin, vitellogenin, storage proteins, and 30 K proteins, were highly acetylated, indicating lysine acetylation may represent a common regulatory mechanism of nutrient utilization in the silkworm. Interestingly, Ser2 proteins, the coating proteins of larval silk, were found to contain many Kac sites, suggesting lysine acetylation may be involved in the regulation of larval silk synthesis. This study is the first to identify the acetylome in a lepidoptera insect, and expands greatly the catalog of lysine acetylation substrates and sites in insects.

Molecular Characterization, Tissue Distribution, Subcellular Localization and Actin-Sequestering Function of a Thymosin Protein from Silkworm

We identified a novel gene encoding a Bombyx mori thymosin (BmTHY) protein from a cDNA library of silkworm pupae, which has an open reading frame (ORF) of 399 bp encoding 132 amino acids. It was found by bioinformatics that BmTHY gene consisted of three exons and two introns and BmTHY was highly homologous to thymosin betas (Tβ). BmTHY has a conserved motif LKHTET with only one amino acid difference from LKKTET, which is involved in Tβ binding to actin. A His-tagged BmTHY fusion protein (rBmTHY) with a molecular weight of approximately 18.4 kDa was expressed and purified to homogeneity. The purified fusion protein was used to produce anti-rBmTHY polyclonal antibodies in a New Zealand rabbit. Subcellular localization revealed that BmTHY can be found in both Bm5 cell (a silkworm ovary cell line) nucleus and cytoplasm but is primarily located in the nucleus. Western blotting and real-time RT-PCR showed that during silkworm developmental stages, BmTHY expression levels are highest in moth, followed by instar larvae, and are lowest in pupa and egg. BmTHY mRNA was universally distributed in most of fifth-instar larvae tissues (except testis). However, BmTHY was expressed in the head, ovary and epidermis during the larvae stage. BmTHY formed complexes with actin monomer, inhibited actin polymerization and cross-linked to actin. All the results indicated BmTHY might be an actin-sequestering protein and participate in silkworm development.

Study of MicroRNAs Related to the Liver Regeneration of the Whitespotted Bamboo Shark, Chiloscyllium plagiosum

To understand the mechanisms of liver regeneration better to promote research examining liver diseases and marine biology, normal and regenerative liver tissues of Chiloscyllium plagiosum were harvested 0 h and 24 h after partial hepatectomy (PH) and used to isolate small RNAs for miRNA sequencing. In total, 91 known miRNAs and 166 putative candidate (PC) miRNAs were identified for the first time in Chiloscyllium plagiosum. Through target prediction and GO analysis, 46 of 91 known miRNAs were screened specially for cellular proliferation and growth. Differential expression levels of three miRNAs (xtr-miR-125b, fru-miR-204, and hsa-miR-142-3p_R-1) related to cellular proliferation and apoptosis were measured in normal and regenerating liver tissues at 0 h, 6 h, 12 h, and 24 h using real-time PCR. The expression of these miRNAs showed a rising trend in regenerative liver tissues at 6 h and 12 h but exhibited a downward trend compared to normal levels at 24 h. Differentially expressed genes were screened in normal and regenerating liver tissues at 24 h by DDRT-PCR, and ten sequences were identified. This study provided information regarding the function of genes related to liver regeneration, deepened the understanding of mechanisms of liver regeneration, and resulted in the addition of a significant number of novel miRNAs sequences to GenBank.

Characterization of a gene encoding prohibitin in silkworm, Bombyx mori.

BACKGROUND Prohibitin (PHB) is an evolutionarily conserved multifunctional protein with ubiquitous expression. However, its molecular roles are largely unknown. METHODS To better understand the function of prohibitin protein in silkworm (BmPHB), its coding sequence was isolated from a cDNA library of silkworm pupae. An His-tagged BmPHB fusion protein was expressed in Escherichia coli Rosetta (DE3) and purified with affinity and reversed-phase chromatography. Purified rBmPHB was used to generate anti-BmPHB polyclonal antibody. The subcellular localization of BmPHB was analysed by immunohistochemistry. RESULTS BmPHB gene has an ORF of 825 bp, encoding a predicted peptide with 274 amino acid residues. Immunostaining indicate that prohibitin is expressed in nucleus and predominately in cytoplasm. Western blot analyses indicated that, in the fifth instar larva, BmPHB was expressed descendingly in gonad, malpighian tubule, trachea, fatty body, intestine, and head. However, no expression was detected in larvas silk gland and epidermis. In addition, BmPHB was expressed in the nascent egg, larva and pupa, but not in the moth. CONCLUSIONS The expression of BmPHB gene presents differential characteristic in different stage and tissues. It may play important roles in the development of silkworm. GENERAL SIGNIFICANCE Studies on prohibitin have been still restricted to a few specific insects and insect cell lines such as Drosophila, Acyrthosiphon pisum and mosquito cell lines, not yet in silkworm. This is a first characterization of prohibitin in silkworm, B. mori.

Lysine acetylation stabilizes SP2 protein in the silkworm Bombyx mori

Lysine acetylation (Kac) is a vital post-translational modification that plays an important role in many cellular processes in organisms. In the present study, the nutrient storage proteins in hemolymph were first found to be highly acetylated-particularly SP2 protein, which contains 20 potential Kac sites. Further results confirmed that lysine acetylation could stabilize and up-regulate the protein level of anti-apoptosis protein SP2, thereby improving the survival of H2O2-treated BmN cells and suppressing the apoptosis induced by H2O2. The potential mechanism involved in the inhibition of ubiquitin-mediated proteasomal degradation by crosstalk between lysine acetylation and ubiquitination. Our results showed that the increase in the acetylation level by TSA could decrease the ubiquitination and improve the protein level of SP2, indicating that lysine acetylation could influence the SP2 protein level through competition between ubiquitination and the suppression of ubiquitin-mediated proteasomal degradation, thereby stabilizing the protein. SP2 is a major nutrient storage protein from hemolymph for amino acid storage and utilization. The crosstalk between lysine acetylation and ubiquitination of SP2 might imply an important role of lysine acetylation for nutrient storage and utilization in silkworm.

Aligning the proteome and genome of the silkworm, Bombyx mori

A technology of mass spectrometry (MS) was used in this study for the large-scale proteomic identification and verification of protein-encoding genes present in the silkworm (Bombyx mori) genome. Peptide sequences identified by MS were compared with those from an open reading frame (ORF) library of the B. mori genome and a cDNA library, to validate the coding attributes of ORFs. Two databases were created. The first was based on a 9× draft sequence of the silkworm genome and contained 14,632 putative proteins. The second was based on a B. mori pupal cDNA library containing 3,187 putative proteins of at least 30 amino acid residues in length. A total of 81,000 peptide sequences with a threshold score of 60% were generated by the MS/MS analysis, and 55,400 of these were chosen for a sequence alignment. By searching these two databases, 6,649 and 250 proteins were matched, which accounted for approximately 45.4% and 7.8% of the peptide sequences and putative proteins, respectively. Further analyses carried out by several bioinformatic tools suggested that the matches included proteins with predicted transmembrane domains (1,393) and preproteins with a signal peptide (976). These results provide a fundamental understanding of the expression and function of silkworm proteins.