We have previously cloned chondroitin 6-sulfotransferase (C6ST) cDNA from chick embryo chondrocytes. C6ST catalyzes sulfation of chondroitin, keratan sulfate, and sialyl N-acetyllactosamine oligosaccharides. In this study, we report the cloning and characterization of a novel sulfotransferase that catalyzes sulfation of keratan sulfate. This new sulfotransferase cDNA clone was obtained from a human fetal brain library by cross-hybridization with chick C6ST cDNA. The cDNA clone obtained contains a single open reading frame that predicts a type II transmembrane protein composed of 411 amino acid residues. When the cDNA was introduced into a eukaryotic expression vector and transfected in COS-7 cells, keratan sulfate sulfotransferase activity was overexpressed, but C6ST activity was not increased over that of the control. Structural analysis of 35 S-labeled glycosaminoglycan, which was formed from keratan sulfate by the reaction with 35 S-labeled 3-phosphoadenosine 5-phosphosulfate and the recombinant sulfotransferase, showed that keratan sulfate was sulfated at position 6 of Gal residues. On the basis of the acceptor substrate specificity, we propose keratan sulfate Gal-6-sulfotransferase (KSGal6ST) for the name of the newly cloned sulfotransferase. KSGal6ST was assigned to chromosome 11p11.1-11.2 by fluorescence in situ hybridization. Among various human adult tissues, a 2.8-kilobase message of KSGal6ST was expressed mainly in the brain. When poly(A) ؉ RNAs from the chick embryo cornea and brain were probed with the human KSGal6ST cDNA in Northern hybridization, a clear band with about 2.8 kilobases was detected. These observations suggest that KSGal6ST may participate in the biosynthesis of keratan sulfate in the brain and cornea.Keratan sulfate proteoglycans (lumican and keratocan) are present in the cornea as the major class of proteoglycan (1, 2) and are thought to play an important role in the corneal transparency (3). A synaptic vesicle membrane glycoprotein, SV2, has been shown to be a keratan sulfate proteoglycan (4). Aggrecan from the cartilage (5) and 3H1 proteoglycan from adult brain (6) contain both chondroitin sulfate and keratan sulfate. Sulfate group of keratan sulfate appears to be important for the biological function of keratan sulfate, because degree of the sulfation of keratan sulfate increased during the corneal development (7, 8) and undersulfated keratan sulfate is synthesized by macular corneal dystrophy (9). Keratan sulfate bears sulfate groups on both GlcNAc and Gal residues. Sulfotransferase activity responsible for the sulfation of keratan sulfate was previously reported (10), but specificity of the enzyme remains obscure because no purified keratan sulfate sulfotransferase (KSST) 1 has so far been obtained. We have previously purified and cloned chondroitin 6-sulfotransferase (C6ST) from the culture medium of chick embryo chondrocytes (11,12). We found that C6ST catalyzes sulfation of chondroitin, keratan sulfate, and sialyl N-acetyllactosamine oligosaccharides (11,13,14). This enzyme...

Lysine-specific demethylase 1 (LSD1/KDM1A) is a histone demethylase and specifically catalyzes the demethylation of mono-and di-methylated histone H3 lysine 4 (H3K4). The LSD1-mediated demethylation of H3K4 promotes the assembly of the c-Myc-induced transcription initiation complex. Although LSD1 and c-Myc are both strongly expressed in human cancers, the mechanisms by which their activities are coordinated remain unclear. We herein demonstrated that LSD1 is a direct target gene of c-Myc. The knockdown of c-Myc decreased the expression of LSD1 in several cancer cell lines. We identified two non-canonical Eboxes in the proximal promoter region of the LSD1 gene. A chromatin immunoprecipitation assay showed that c-Myc bound to these E-boxes in the LSD1 promoter. Importantly, LSD1 mRNA expression correlated with c-Myc expression in human acute myeloid leukemia (AML), glioblastoma, stomach adenocarcinoma, and prostate adenocarcinoma. The present results suggest that LSD1 is induced by c-Myc and forms a positive feedback mechanism in transcription reactions by c-Myc.

Tribbles related homolog 1 is the mammalian ortholog of Tribbles, which controls cell division and migration during development in Drosophila. TRB1 is a pseudokinase and functions as a scaffold protein. Recent findings suggest that TRB1 plays important roles in hepatic lipid metabolism and participates in insulin resistance. However, the underlying mechanisms have not yet been elucidated. Here, we demonstrate that TRB1 suppresses FOXO1 transcriptional activity to downregulate the expression of G6Pase and PEPCK, which encode gluconeogenic rate‐limiting enzymes. TRB1 knockdown enhances FOXO1 binding to the gluconeogenic gene promoters. It also increases FOXO1 acetylation and recruits CBP to the binding sequence of FOXO1. These results suggest that TRB1 suppresses the expression of G6Pase and PEPCK by attenuating FOXO1 transcriptional activity and negatively regulates gluconeogenesis.