A novel 14-base-pair regulatory element is essential for in vivo expression of murine beta4-galactosyltransferase-I in late pachytene spermatocytes and round spermatids

A-MYB (MYBL1) stimulates murine testis-specific Ldhc expression via the cAMP-responsive element (CRE) site

Generally, knowledge of the mechanism regulating gene expression in primary spermatocytes is incomplete. We have used the lactate dehydrogenase gene (Ldhc) as a model to explore these mechanisms during spermatogenesis. Its 100-bp core promoter contained two essential elements common to many genes, a GC box and a CRE site. Here we report results that support a model in which transcription factor MYBL1 acts as a coactivator directing tissue-specific expression via the CRE cis element. We hypothesize that this is a common mechanism involving activation of multiple genes in the primary spermatocyte. MYBL1 is expressed predominantly as a tissue-specific transcription factor in spermatocytes and breast epithelial cells. Our finding that LDHC expression is lost in 21-day testes of MYBL1 mutant mice supports our hypothesis. In the GC1-spg germ cell line exogenous MYBL1 induces activity 4- to 8-fold, although extracts from these cells do not show MYBL1 binding activity for the Myb consensus sequences in the Ldhc promoter by EMSA. Rather, MYBL1 stimulates expression from a synthetic promoter containing only CRE elements, suggesting MYBL1 activates the promoter by interacting with protein that binds to a CRE element. Mutation of three Myb sites does not affect Ldhc promoter activity significantly (P > 0.05). CREB-binding protein (CBP) is a coactivator that interacts with CRE-binding protein CREB. We show that the transactivation domain (TAD) in MYBL1 interacts with the KIX domain in CBP, and the TAD domain and DNA binding domain in MYBL1 each interact with the CREB N-terminal domain. MYBL1 also stimulated expression from testis-specific genes Pgk2 (phosphoglycerate kinase 2) and Pdha2 (pyruvate dehydrogenase alpha 2) promoters, each of which contains CRE promoter elements and is expressed in primary spermatocytes. We propose that MYBL1 directs germ cell-specific activation via the CRE site of certain genes that are activated specifically in the primary spermatocyte, although other, more indirect effects of MYBL1 remain a possible explanation for our results.

Functional cooperation between CREM and GCNF directs gene expression in haploid male germ cells

Cellular differentiation and development of germ cells critically depend on a coordinated activation and repression of specific genes. The underlying regulation mechanisms, however, still lack a lot of understanding. Here, we describe that both the testis-specific transcriptional activator CREMτ (cAMP response element modulator tau) and the repressor GCNF (germ cell nuclear factor) have an overlapping binding site which alone is sufficient to direct cell type-specific expression in vivo in a heterologous promoter context. Expression of the transgene driven by the CREM/GCNF site is detectable in spermatids, but not in any somatic tissue or at any other stages during germ cell differentiation. CREMτ acts as an activator of gene transcription whereas GCNF suppresses this activity. Both factors compete for binding to the same DNA response element. Effective binding of CREM and GCNF highly depends on composition and epigenetic modification of the binding site. We also discovered that CREM and GCNF bind to each other via their DNA binding domains, indicating a complex interaction between the two factors. There are several testis-specific target genes that are regulated by CREM and GCNF in a reciprocal manner, showing a similar activation pattern as during spermatogenesis. Our data indicate that a single common binding site for CREM and GCNF is sufficient to specifically direct gene transcription in a tissue-, cell type- and differentiation-specific manner.

Regulation of murine lactate dehydrogenase C (Ldhc) gene expression

Expression of Ldhc begins with the onset of meiosis in male germ cells and continues throughout spermatogenesis. Transcriptional regulatory mechanisms, especially in primary spermatocytes, are poorly described because of the lack of a reliable cell culture system. We constructed mouse transgenics and transfected germ cells in situ to study expression of the testis-specific isozyme of lactate dehydrogenase (LDH). From previous work, we determined that a 100-bp Ldhc core promoter contained potential cis regulatory elements, including a palindrome (-21 to +10), GC box (-70 to -65), and cAMP-responsive element (CRE) sites (-53 to -49, -39 to -35). We provide here the demonstration of a functional role for these sequences by expression of mutated transgenes in vivo. Our results reveal for the first time that mutation of the GC box does not abolish promoter activity, which remains testis-specific. Mutation of GC box or CRE sites resulted in a 73% and 74% reduction in promoter activity, respectively, in a transient transfection of germ cells in vivo by electroporation; the combination of GC box and CRE site mutations eliminates promoter activity. Therefore, we conclude that simultaneous occupancy of the GC box and CRE sites in the core promoter is necessary for full expression of Ldhc in the testis.

Sequential action of Ets-1 and Sp1 in the activation of the human beta-1,4-galactosyltransferase V gene involved in abnormal glycosylation characteristic of cancer cells

Malignant transformation is associated with increased gene expression of beta-1,4-galactosyltransferase (beta-1,4-GalT) V, which contributes to the biosynthesis of highly branched N-linked oligosaccharides characteristic of cancer cells. Our previous study showed that expression of the human beta-1,4-GalT V gene is regulated by Sp1 (Sato, T., and Furukawa, K. (2004) J. Biol. Chem. 279, 39574-39583), and a subsequent study showed that the gene expression is also activated by Ets-1, a product of the oncogene (Sato, T., and Furukawa, K. (2005) Glycoconj. J. 22, 365). Herein we report the mechanism of beta-1,4-GalT V gene activation by these transcription factors. The gene expression and promoter activity of beta-1,4-GalT V increased when the ets-1 cDNA was transfected into A549 cells, which contain a small amount of Ets-1, but decreased dramatically when the dominant-negative ets-1 cDNA was transfected into HepG2 cells, which contain a large amount of Ets-1. Luciferase assays using deletion constructs of the beta-1,4-GalT V gene promoter showed that promoter region -116 to +22 is critical for the transcriptional activation of the gene by Ets-1. Despite the presence of one Ets-1-binding site, which overlapped the Sp1-binding site, electrophoretic mobility shift assays showed that the region bound preferentially to Sp1 rather than to Ets-1. To solve this problem, we examined the transcriptional regulation of the human Sp1 gene by Ets-1 and found that the gene expression and promoter activity of Sp1 are regulated by Ets-1 in cancer cells. Functional analyses of two Ets-1-binding sites in the Sp1 gene promoter showed that only Ets-1-binding site -413 to -404 is involved in the activation of the gene by Ets-1. These results indicate that Ets-1 enhances expression of the beta-1,4-GalT V gene through activation of the Sp1 gene in cancer cells.

cis-requirement for the maintenance of round spermatid-specific transcription

Maintenance of strict developmental stage- and cell type-specific gene expression is critical for the progression of spermatogenesis. However, the mechanisms which sustain the spatiotemporal order of gene transcription within the seminiferous epithelium are poorly understood. Previous work has established that the proximal promoter of the mouse SP-10 gene was sufficient to maintain round spermatid-specific expression (Reddi, P.P., Shore, A.N., Shapiro, J.A., Anderson, A., Stoler, M.H., Acharya, K.K., 2003b. Spermatid-specific promoter of the SP-10 gene functions as an insulator in somatic cells. Dev. Biol. 262, 173-182). The present study addressed the cis-requirement for this regulation and sought to identify the cognate transcription factor(s). We found that mutation of two 5'-ACACAC motifs (at -172 and -160) within the -186/+28 SP-10 promoter led to premature and indiscriminate expression of a reporter gene in the seminiferous epithelium of transgenic mice, whereas the wild-type -186/+28 promoter retained spermatid specificity. Neither promoter showed ectopic expression in the somatic tissues. Expression cloning using the -186/-148 portion of the promoter yielded transcriptional repressors TDP-43 and Puralpha of which TDP-43 required the complementary 5'-GTGTGT elements located on the opposite strand for binding in vitro. Further, Northern analysis and immunohistochemistry of mouse testis showed the presence of TDP-43 in cell-types where the SP-10 gene remains repressed. Taken together, our results demonstrate that 5'-GTGTGT motifs on the complementary strand are required to prevent premature expression of SP-10 during spermatogenesis and implicate TDP-43 as the putative regulatory factor. The study also implied that additional level(s) of regulation keep the SP-10 gene silent in the somatic tissues.

The cis-regulatory element Gsl5 is indispensable for proximal straight tubule cell-specific transcription of core 2 beta-1,6-N-acetylglucosaminyltransferase in the mouse kidney

Gsl5 regulates the expression of a glycolipid and glycoproteins that contain the Le(X) epitope in the mouse kidney through tissue-specific transcriptional regulation of the core 2 beta-1,6-N-acetylglucosaminyltransferase (core 2 GnT) gene. The core 2 GnT gene has six exons and produces three alternatively spliced transcripts. Gsl5 regulates only the expression of the kidney-type mRNA, which is transcribed from the most 5'-upstream exon. By introducing a 159-kb bacterial artificial chromosome (BAC) clone that carries the mouse core 2 GnT gene and its 5'-upstream region into DBA/2 mice that carry a defective Gsl5 allele, we were able to rescue the deficient phenotype. The BAC clone was subsequently engineered to replace the core 2 GnT gene with the sequence of enhanced green fluorescent protein (EGFP) as a reporter by an inducible homologous recombination system in Escherichia coli. The transgenic mice derived from the modified BAC clone expressed EGFP in the kidney, which suggests that the candidate Gsl5 is in the 5'-upstream region of the core 2 GnT gene. Sequence analysis of the 5'-upstream regions of the BAC clone and DBA/2 genomic DNA revealed a candidate sequence for Gsl5 at about 5.5 kb upstream of exon 1. This sequence consisted of eight repeats of two GT-rich units in the wild-type mice, whereas it consisted of only one pair of GT-rich units with a minor modification in the DBA/2 mice. Transgenic mice produced with the EGFP reporter gene construct that included this candidate sequence expressed EGFP exclusively in the proximal straight tubular cells of the kidney. These results indicated that this unique repeat is indeed the Gsl5, and it is a cis-regulatory element responsible for proximal straight tubule cell-specific transcriptional regulation.

ETS-1 transcription factor activates the expression of mouse UDP-Gal:GA2/GM2/GD2/GT2 galactosyltransferase gene

UDP-Gal:GA2/GM2/GD2/GT2 galactosyltransferase (Gal-T2) transfers galactose to the terminal N-acetylgalactosamine of either the neutral glycolipid GA2 or of the gangliosides GM2, GD2 and GT2. Previous studies revealed a tight regulation of Gal-T2 activity and mRNA expression during development of the rat CNS. Here, we study in PC12 cells the cis-acting elements involved in the activation of a fragment of 211 bp around the transcription initiation site of the mouse Gal-T2 promoter. Mutagenesis, competition experiments and functional assays showed that the Ets-1 transcription factor is involved in the activation of the Gal-T2 promoter.

Basic helix-loop-helix transcription factor Tcfl5 interacts with the Calmegin gene promoter in mouse spermatogenesis

In mouse spermatogenesis, differentiating germ line cells initiate expression of specific genes at subsequent developmental steps. The Calmegin (Clgn) gene is first expressed in meiotic prophase, in primary spermatocytes, and encodes a protein that acts as a chaperone. To identify testis-specific transcription factors that control expression of the Clgn gene in spermatogenesis, we performed a yeast one-hybrid screening with a Clgn promoter sequence as bait DNA. This screening resulted in the identification of mouse Tcfl5 as a candidate Clgn promoter-binding protein. Tcfl5 is a member of the basic helix-loop-helix (bHLH) family of transcription factors, and mouse Tcfl5 shows 83% amino acid sequence identity with human TCFL5. Gel-shift and yeast one-hybrid experiments showed that Tcfl5 interacts with a non-canonical CACGCG site that is present in the Clgn promoter. By using northern blot, RT-PCR and in situ hybridization, mouse Tcfl5 mRNA was detected only in testis, with the highest expression level in primary spermatocytes and round spermatids. The highest level of Tcfl5 protein was found in primary spermatocytes at the diplotene stage of meiotic prophase, where the protein colocalizes with transcriptionally active chromatin.

A Short Core Promoter Drives Expression of the ALF Transcription Factor in Reproductive Tissues of Male and Female Mice1

The control of gene expression in reproductive tissues involves a number of unique germ cell-specific transcription factors. One such factor, ALF (TFIIA tau), encodes a protein similar to the large subunit of general transcription factor TFIIA. To understand how this factor is regulated, we characterized transgenic mice that contain the ALF promoter linked to either beta-galactosidase or green fluorescent protein (GFP) reporters. The results show that as little as 133 base pairs are sufficient to drive developmentally accurate and cell-specific expression. Transgene DNA was methylated and inactive in liver, but could be reactivated in vivo by system administration of 5-aza, 2'-deoxycytidine. Fluorescence-activated cell sorting allowed the identification of male germ cells that express the GFP transgene and provides a potential method to collect cells that might be under the control of a nonsomatic transcription system. Finally, we found that transcripts from the endogenous ALF gene and derived transgenes can also be detected in whole ovary and in germinal vesicle-stage oocytes of female mice. The ALF sequence falls into a class of germ cell promoters whose features include small size, high GC content, numerous CpG dinucleotides, and an apparent TATA-like element. Overall, the results define a unique core promoter that is active in both male and female reproductive tissues, and suggest mouse ALF may have a regulatory role in male and female gametogenic gene expression programs.

Transcriptional Regulation of the Human β-1,4-Galactosyltransferase V Gene in Cancer Cells

Beta-1,4-galactosyltransferase (beta-1,4-GalT) V is a constitutively expressed enzyme that can effectively galactosylate the GlcNAcbeta1-->6Man group of the highly branched N-glycans that are characteristic of tumor cells. Upon malignant transformation of cells, the expression of the beta-1,4-GalT V gene increases in accordance with the increase in the amounts of highly branched N-glycans. Lectin blot analysis showed that the galactosylation of highly branched N-glycans is inhibited significantly in SH-SY5Y human neuroblastoma cells by the transfection of the antisense beta-1,4-GalT V cDNA, indicating the biological importance of the beta-1,4-GalT V for the functions of highly branched N-glycans. We cloned the 2.3-kb 5'-flanking region of the human beta-1,4-GalT V gene, and we identified the region -116/-18 relative to the transcription start site as that having promoter activity. The region was found to contain several putative binding sites for transcription factors, including AP2, AP4, N-Myc, Sp1, and upstream stimulatory factor. Electrophoretic mobility shift assay showed that Sp1 binds to nucleotide positions -81/-69 of the promoter region. Mutations induced in the Sp1-binding site showed that the promoter activity of the beta-1,4-GalT V gene is impaired completely in cancer cells. In contrast, the promoter activity increased significantly by the transfection of the Sp1 cDNA into A549 human lung carcinoma cells. Mithramycin A, which inhibits the binding of Sp1 to its binding site, reduced the promoter activation and expression of the beta-1,4-GalT V gene in A549 cells. These results indicate that Sp1 plays an essential role in the transcriptional activity of the beta-1,4-GalT V gene in cancer cells.

Identification of a short PIASx gene promoter that directs male germ cell-specific transcription in vivo

PIASx gene encodes two SUMO E3 ligases that are highly expressed in the testis. We have isolated and analyzed the promoter of the murine PIASx gene. Electrophoretic mobility shift assays with testicular nuclear extracts showed that the proximal promoter forms a major DNA-protein complex containing Sp1, Sp2, and Sp3 transcription factors. Reporter gene assays in cultured cells indicated that a fragment comprising nucleotides from -168 to +76 relative to transcription start site is sufficient for basal promoter activity in cultured cells, but these in vitro assays failed to reveal clear differences in promoter activity between testis- and non-testis-derived cell lines. Interestingly, however, the proximal promoter encompasses the elements necessary for a testis-specific transcription in vivo, as it directed beta-galactosidase expression exclusively to male germ cells in transgenic mice. In conclusion, we have characterized the minimal PIASx promoter that can be used for highly specific targeting of transgene expression to male germ cells.

A 3-kilobase region derived from the rat cathepsin L gene directs in vivo expression of a reporter gene in sertoli cells in a manner comparable to that of the endogenous gene

During mammalian spermatogenesis, the transcription of several genes in Sertoli cells is turned on and off as the adjacent male germ cells progress through the stages of the cycle of the seminiferous epithelium. A requirement for defining how germ cells regulate this process is the identification of a promoter that confers, in vivo, accurate, stage-specific gene expression in Sertoli cells. To date, such a promoter has not been identified. Using transgenic mice, we show that the 3-kilobase genomic fragment immediately upstream of the rat cathepsin L translation start site directs expression of the reporter gene, beta-galactosidase, only in Sertoli cells. The expression pattern of the reporter gene recapitulated that of the endogenous gene in Sertoli cells as 75% of the seminiferous tubules that contained X-gal positive Sertoli cells were at stages VI-VIII and beta-galactosidase enzymatic activity was 4-fold higher in mature testes compared with immature testes. This is, to our knowledge, the first identification of a promoter region that contains all of the regulatory elements required for accurate, stage-specific gene expression in Sertoli cells.

Characterization of the promoter region of the human Galbeta1,3(4)GlcNAc alpha2,3-sialyltransferase III (hST3Gal III) gene

Multiple promoters are found in the hST3Gal IV, hST3Gal V and hST3Gal VI genes. These promoters may respond to different physiological signals and stimuli in different cell types. The multiple regulatory pathways of these ubiquitous sialyltransferases may need to be differentially modulated in various cell types. Here, we report transcriptional regulation of the hST3Gal III gene. 5'-RACE analysis determined that the transcription initiation sites map at -181 bp from the translation initiation site in all four cell lines (K-562, HT-29, PC-3 and HepG2) tested. Our results suggest that the hST3Gal III gene does not have multiple mRNAs, as have been identified for the hST3Gal IV, hST3Gal V and hST3Gal VI genes. The 5'-untranslated region was found to be divided into two exons, E1 and E2, indicating that the transcriptional regulation of hST3Gal III depends on the pIII promoter that exists 5'-upstream of exon E1. Luciferase assay results suggest that the nt -303 to -1 region is important for transcriptional activity of the hST3Gal III gene in all four cell lines tested. These results suggest that ubiquitous factors, such as Sp1, may be important for hST3Gal III gene expression.

Determination of the half-life of the murine beta4-galactosyltransferase-1 mRNA in somatic cells using the tetracycline-controlled transcriptional regulation system

The glycosyltransferases are recognized as a functional family of an estimated 300 distinct, intracellular, membrane-bound enzymes that are positioned along the secretory pathway and participate coordinately in the biosynthesis of the carbohydrate moieties on glycoconjugates. The full-length cDNA sequence for many of these proteins is now available yet little is known about the transcriptional or translational regulation of a given transcript or its decay rate in the cell. These issues are made more complex by the observations that transcription of a glycosyltransferase gene in different cells/tissues results in mRNAs with significantly different structures. For example, transcription of the murine beta4-galactosyoltransferase-1 gene in somatic cells yields two transcripts of 3.9 and 4.1 kb. In contrast transcription of this gene in developing male germ cells results in transcripts of 2.9 and 3.1 kb which are distinguished from their somatic cell counterparts primarily by the deletion of approximately 1.7 kb of sequence in the 3'-untranslated region (UTR). With the long range goal of determining the role that the 3'-UTR serves in mRNA decay we have taken advantage of a recently developed methodology, the Tet-Off system, to determine the half-life of the mRNA encoding beta4-galactosyltransferase-1 in the murine NIH 3T3 somatic cell line. We show that the beta4-galactosyltransferase-1 mRNA has a half-life of approximately 84 min (range of 82-85 min) in 3T3 cells and that substitution of the galactosyltransferase coding sequence with the coding sequence of luciferase does not significantly alter the decay rate (approximately 87 min; range of 84-91 min). This latter observation suggests that the beta4-galactosyltransferase-1 coding sequence does not contain functional elements that affect the intrinsic stability of this mRNA.

Transcriptional regulation of human Galbeta1,3GalNAc/Galbeta1, 4GlcNAc alpha2,3-sialyltransferase (hST3Gal IV) gene in testis and ovary cell lines

The mRNA expression of sialyltransferase genes is regulated in a cell-type-specific manner. The mRNAs of human Galbeta1, 3GalNAc/Galbeta1, 4 GlcNAc alpha2,3-sialyltransferase gene (hST3Gal IV) consist of six isoforms, type A1, A2, B1, B2, B3, and BX. These mRNAs are transcribed from different promoters, pA, pB1, pB2, pB3, and pBX, respectively. Type B mRNAs are expressed in several cells, whereas type A mRNAs are specifically expressed in testis, ovary, and placenta, suggesting that pA promoter activity is especially high in these tissues. We show herein germ-cell specific transcriptional regulation of the hST3Gal IV pA promoter. Using a luciferase assay, pA promoter activity is shown to be high in testis and ovary cell lines. We identified the enhancer region of the pA promoter, located at nt -520 to -420. These results suggest that this element plays a critical role in germ-cell specific regulation of the pA promoter. The results of site-directed mutagenesis suggest that AP2 and c-Ets sites in this region are involved in pA promoter activity, which in turn suggests that the hST3Gal IV gene is regulated in a tissue-restricted fashion at the level of transcription.

Molecular cloning, gene organization, and expression of mouse Mpi encoding phosphomannose isomerase

Phosphomannose isomerase (PMI) interconverts fructose-6-P (Fru-6-P) and mannose-6-P (Man-6-P), linking energy metabolism to protein glycosylation. We have cloned the mouse Mpi cDNA, analyzed its genomic organization, and studied the expression in different tissues. The Mpi gene has eight exons covering 7.2 kb. The structure and intron-exon boundaries are essentially the same as its human ortholog with 85% amino acid identity. Mpi is alternatively spliced at the 3' end, resulting in three messages with different 3'-untranslated regions. Mpi expression is regulated at both the transcription and translation levels, with the highest expression level in testis. Rabbit antibodies prepared against mouse PMI expressed in E. coli recognize a single 47-kDa band. Immunohistochemistry of mouse tissues shows general cytosolic staining in all cells. In testis, staining is intense in round spermatids and residual bodies, moderate in pachytene spermatocytes, and weak in spermatogonia and spermatozoa. In contrast, northern blot analysis shows comparable transcripts of 1.8 and 1.6 kb in pachytene spermatocytes and round spermatids, suggesting delayed translation of PMI. The stage-specific expression of PMI in testis may be important for KDN synthesis, which requires Man-6-P, or it may be needed to ensure sufficient glycosylation precursors in cells that do not utilize glucose and instead rely on lactate and pyruvate.

Testis hormone-sensitive lipase expression in spermatids is governed by a short promoter in transgenic mice

A testicular form of hormone-sensitive lipase (HSL(tes)), a triacylglycerol lipase, and cholesterol esterase, is expressed in male germ cells. Northern blot analysis showed HSL(tes) mRNA expression in early spermatids. Immunolocalization of the protein in human and rodent seminiferous tubules indicated that the highest level of expression occurred in elongated spermatids. We have previously shown that 0.5 kilobase pairs of the human HSL(tes) promoter directs testis-specific expression of a chloramphenicol acetyltransferase reporter gene in transgenic mice and determined regions binding nuclear proteins expressed in testis but not in liver (Blaise, R., Grober, J., Rouet, P., Tavernier, G., Daegelen, D., and Langin, D. (1999) J. Biol. Chem. 274, 9327-9334). Mutation of a SRY/Sox-binding site in one of the regions did not impair in vivo testis-specific expression of the reporter gene. Further transgenic analyses established that 95 base pairs upstream of the transcription start site were sufficient for correct testis expression. In gel retardation assays using early spermatid nuclear extracts, a germ cell-specific DNA-protein interaction was mapped between -46 and -29 base pairs. The DNA binding nuclear protein showed properties of zinc finger transcription factors. Mutation of the region abolished reporter gene activity in transgenic mice, showing that it is necessary for testis expression of HSL(tes).

Human alpha (1,3)-fucosyltransferase IV (FUTIV) gene expression is regulated by elk-1 in the U937 cell line

The alpha1,3-fucosyltransferase IV (FucTIV) encoded by its gene (FUTIV) is responsible for synthesis of Le(x) (Galbeta4[Fucalpha3]GlcNAcbeta3Galbeta1,R), which causes compaction in the morula stage of the preimplantation mouse embryo, as well as alpha1,3-fucosylation at multiple internal GlcNAc of unbranched poly-N-acetyllactosamine, termed "myeloglycan," the physiological epitope of E-selectin. Since myeloglycan-type structure is also expressed in various types of human cancer and may mediate E-selectin-dependent metastasis, expression of FUTIV is oncodevelopmentally regulated. The mechanisms controlling FUTIV expression remain to be clarified. In this report, we further characterize FUTIV gene structure and define a non-TATA box-dependent transcriptional start region just upstream from the translational start. FUTIV promoter/reporter fusion constructs defined a "full-length" promoter and highly active fragments in the macrophage-derived U937 and myeloid HL60 cell lines. One highly active fragment contains a consensus binding site for the Ets-1 transcription factor (Withers, D. A., and Hakomori, S. (1997) Glycoconj. J. 14, 764). Gel shift analysis shows specific binding to this site in nuclear extracts from U937 cells. Mutation of the Ets consensus site significantly reduces FUTIV promoter activity in both cell lines. Gel supershift and dominant negative cotransfection experiments identified the Ets family member Elk-1 as one component binding and regulating the FUTIV promoter in U937 cells. The significance of FUTIV regulation by Elk-1 is discussed.

Lessons from knockout and transgenic mice for infertility in men

This review concentrates on the clear cases where knocking out a gene in mice has caused male infertility and thus comes near to proving that the gene plays a role in the development of sperm. Knockout mice have been created with primary defects at every stage of spermatogenesis thus creating a framework for decoding the genetic hierarchy that causes male germ cell differentiation. As well as defining essential genes in vivo experiments have defined promoter and untranslated sequences responsible for the expression of proteins at all the spermatogenic stages. In conclusion knockout mice remain the ultimate test of spermatogenic hypotheses as well as providing detailed information about this complex process.

Phorbol ester treatment of HL 60 leukemia cells results in increase of beta-(1 --> 4)-galactosyltransferase

We previously showed that HL 60 leukemia cells exhibit various changes in their cellular glycans after phorbol 12-myristate 13-acetate (PMA) treatment. These changes could originate largely from changes in one or several glycosyltransferases. In this report, we show using enzymatic measures, fluorescence microscopy, immunoblotting and Northern blot that beta-(1 --> 4)-galactosyltransferase I (GalT I) activity was higher (> x 2) in PMA-treated compared with untreated HL 60 cells. Immunoblotting showed an increased intensity of the GalT I band at 49 kDa and Northern blot a weak increase of the GalT I transcript band, after PMA treatment. Moreover, Northern blot performed after actinomycin-D treatment of the cells, which inhibits transcription, suggests that the observed increase of GalT I expression could originate, in part, from increase of the stability of GalT I transcripts.

Regulation of expression of the human beta-1,2-N-acetylglucosaminyltransferase II gene (MGAT2) by Ets transcription factors

Oncogenic transformation of fibroblasts by the src oncogene has long been known to cause an increase in the size of cell-surface protein-bound oligosaccharides, owing primarily to increased N-glycan branching mediated by increased beta-1,6-N-acetylglucosaminyltransferase V (GnT V) activity. The src-responsive element of the GnT V promoter was localized to Ets-binding sites and the promoter was transcriptionally stimulated by both ets-1 and ets-2 expression [Buckhaults, Chen, Fregien and Pierce (1997) J. Biol. Chem. 272, 19575-19581; Kang, Saito, Ihara, Miyoshi, Koyama, Sheng and Taniguchi (1996) J. Biol. Chem. 271, 26706-26712]. Because GnT V action requires the prior action of beta-1,2-N-acetylglucosaminyltransferase II (GnT II) and the human GnT II promoter contains four putative Ets-binding sites [Chen, Zhou, Tan and Schachter (1998) Glycoconj. J. 15, 301-308], GnT II might also be under oncogenic control via Ets transcription factors. We now report that co-transfection into HepG2 or COS-1 cells of either ets-1 or ets-2 expression plasmids together with chimaeric GnT II promoter-chloramphenicol acetyltransferase plasmids results in a 2-4-fold stimulation of promoter activity. Mobility-shift assays and South-Western blots localized the functional Ets-binding site to one of the four putative sites on the GnT II promoter. The GnT II promoter, unlike the GnT V promoter, is not activated by either src or neu. Therefore although both promoters are stimulated by a member of the Ets family of transcription factors, the functional role of this Ets transcriptional control seems to be different for the two genes.