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BCL2L12, a newly identified member of Bcl-2 family, and its transcript variant BCL2L12A have been found to be associated with favorable prognosis in breast cancer patients while correlated with tumorigenesis of glioblastoma and colon cancer. However, the biological functions of BCL2L12 and especially those of BCL2L12A are largely unknown. Here, we report that, unlike other Bcl-2 family proteins, BCL2L12 and its transcript variant BCL2L12A are nuclear proteins. Interestingly, BCL2L12 forms speckle patterns in the nuclei and potently induces apoptosis in CHO cells. BCL2L12A had a diffuse distribution in the nuclei and inhibits cell growth by inducing cell cycle arrested at G2/M transition in CHO cells. More importantly, BCL2L12A-induced G2/M arrest was associated with a slight up-regulation of cyclin B1 and significant down-regulation of an active form of cyclin B1 phosphorylated at Ser147. Taken together, our study suggests that both BCL2L12 and BCL2L12A have negative effects on CHO cell growths, and that BCL2L12A is a potential cell cycle regulator that interferes with G2-M transition.

Previous study indicated that beta1,4-galactosyltransferase I (beta1,4GT1) was up-regulated by cycloheximide (CHX) and thus enhanced apoptosis induced by CHX in SMMC-7721 cells. In this study, we reported that constitutively active Akt protein (myr-Akt) inhibited CHX-induced apoptosis in SMMC-7721 cells through down-regulating beta1,4GT1. However, the two PI3K inhibitors LY294002 and wortmannin treatment up-regulated beta1,4GT1 through enhancing Sp1 protein expression and consequently increased CHX-induced SMMC-7721 cells apoptosis. Besides, our results suggested that beta1,4GT1 and cell surface galactose residues synthesized by elevated beta1,4GT1 played an important role in SMMC-7721 cells apoptosis treated with CHX and PI3K inhibitor together. Moreover, we found that CHX accentuated beta1,4GT1 through down-regulating Akt expression to mediate SMMC-7721 cells apoptosis. Taken together, PI3K inhibitors LY294002 and wortmannin up-regulated beta1,4GT1 and enhanced CHX-induced apoptosis in SMMC-7721 cells, which suggested that PI3K inhibitors might have therapeutic potential when combined with CHX in the treatment of hepatoma.

Glycosylation is one of the most important post-translational modifications and it is clear that the single step of β-1,4-galactosylation is performed by a family of β-1,4-galactosyltransferases (β4-GalTs) and that each member of this family may play a distinct role in different tissues and cells. In this study, we characterized the gene expression of six β4-GalTs in mouse testis and analyzed the changes of galactosylation of testis glycoproteins during postnatal development. Northern blot analysis revealed that β4-GalT-I and β4-GalT-IV were expressed mainly in newborn mouse testis and that the expression of β4-GalT-II increased markedly and persisted at the highest levels in adult mouse testis. The expression of β4-GalT-III and β4-GalT-V, however, remained relatively at low levels during mouse testicular development. In contrast, the expression of β4-GalT-VI was undetectable in mouse testis. The gene expression of β4-GalT-II in mouse testis was further analyzed by in situ hybridization due to its unique expression pattern. Strong hybridization signals were detected in the seminiferous tubules and the expression varied among the different stages of spermatogenic differentiation. The distinct gene expression patterns of β4-GalTs in mouse testis could affect the differential galactosylation of testis glycoproteins, as revealed by lectin histochemistry analysis.

CDK11(p58), a G2/M-specific protein kinase, has been shown to be associated with apoptosis in many cell lines, with largely unknown mechanisms. Our previous study proved that CDK11(p58)-enhanced cycloheximide (CHX)-induced apoptosis in SMMC-7721 hepatocarcinoma cells. Here we report for the first time that ectopic expression of CDK11(p58) down-regulates Bcl-2 expression and its Ser70, Ser87 phosphorylation in CHX-induced apoptosis in SMMC-7721 cells. Overexpression of Bcl-2 counteracts the pro-apoptotic activity of CDK11(p58). Furthermore, we confirm that the kinase activity of CDK11(p58) is essential to the down-regulation of Bcl-2 as well as apoptosis. Taken together, these results demonstrate that CDK11(p58) down-regulates Bcl-2 in pro-apoptosis pathway depending on its kinase activity, which elicits survival signal in hepatocarcinoma cells.

The human trihydrophobin 1 (TH1) is a highly conserved and widely expressed protein. It is clear that TH1 serves as a new specific negative regulator of A-Raf kinase. In this study, we found that TH1 associated with A-Raf in mouse testis by using coimmunoprecipitation analysis. Then we characterized the gene expression of TH1 in mouse testis and analyzed the changes of TH1 protein during postnatal development. The protein expression of TH1 in mouse testis was further analyzed by immunohistochemistry staining. Strong signals were detected in the seminiferous tubules and the distribution patterns varied with the different ages of postnatal mouse testis. TH1 was distributed in spermatocytes and Sertoli cells at 2 weeks postnatal, and was abundant in spermatogonia at 8 weeks postnatal. Leydig cells were positive to TH1 throughout testicular development. A high expression of TH1 in both Leydig cells and mouse Leydig tumor cells (mLTC-1cells) was found to be concentrated in the cytoplasm. The colocalization of TH1 and A-Raf in mLTC-1 cells or in adult testis was also observable.

Our previous studies have shown that overexpression of beta1,4-galactosyltransferase1 (beta1,4GT1) leads to increased apoptosis induced by cycloheximide (CHX) in SMMC-7721 human hepatocarcinoma cells. However, the role of beta1,4GT1 in apoptosis remains unclear. Here we demonstrated that cell surface beta1,4GT1 inhibited the autophosphorylation of epidermal growth factor receptor (EGFR) especially at Try 1068. The phosphorylation of protein kinase B (PKB/Akt) and extracellular signal-regulated protein kinase1/2 (ERK1/2), which are downstream molecules of EGFR, were also reduced in cell surface beta1,4GT1-overexpressing cells. Furthermore, the translocations of Bad and Bax that are regulated by PKB/Akt and ERK1/2 were also increased in these cells. As a result, the release of cytochrome c from mitochondria to cytosol was increased and caspase-3 was activated. In contrast, RNAi-mediated knockdown of beta1,4GT1 increased the autophosphorylation of EGFR. These results demonstrated that cell surface beta1,4GT1 may negatively regulate cell survival possibly through inhibiting and modulating EGFR signaling pathway.

Glycosylation is one of the most important post-translational modifications and it is clear that the single step of beta-1,4-galactosylation is performed by a family of beta-1,4-galactosyltransferases (beta4-GalTs) and that each member of this family may play a distinct role in different tissues and cells. In this study, we characterized the gene expression of six beta4-GalTs in mouse testis and analyzed the changes of galactosylation of testis glycoproteins during postnatal development. Northern blot analysis revealed that beta4-GalT-I and beta4-GalT-IV were expressed mainly in newborn mouse testis and that the expression of beta4-GalT-II increased markedly and persisted at the highest levels in adult mouse testis. The expression of beta4-GalT-III and beta4-GalT-V, however, remained relatively at low levels during mouse testicular development. In contrast, the expression of beta4-GalT-VI was undetectable in mouse testis. The gene expression of beta4-GalT-II in mouse testis was further analyzed by in situ hybridization due to its unique expression pattern. Strong hybridization signals were detected in the seminiferous tubules and the expression varied among the different stages of spermatogenic differentiation. The distinct gene expression patterns of beta4-GalTs in mouse testis could affect the differential galactosylation of testis glycoproteins, as revealed by lectin histochemistry analysis.