The cdc25+ tyrosine phosphatase is a key mitotic inducer of the fission yeast Schizosaccharomyces pombe, controlling the timing of the initiation of mitosis. Mammals contain at least three cdc25+ homologues called cdc25A, cdc25B and cdc25C. In this study we investigate the biological function of cdc25A. Although very potent in rescuing the S.pombe cdc25 mutant, cdc25A is less structurally related to the S.pombe enzyme. Northern and Western blotting detection reveals that unlike cdc25B, cdc25C and cdc2, cdc25A is predominantly expressed in late G1. Moreover, immunodepletion of cdc25A in rat cells by microinjection of a specific antibody effectively blocks their cell cycle progression from G1 into the S phase, as determined by laser scanning single cell cytometry. These results indicate that cdc25A is not a mitotic regulator but a novel phosphatase that plays a crucial role in the start of the cell cycle. In view of its strong ability to activate cdc2 kinase and its specific expression in late G1, cdc2‐related kinases functioning early in the cell cycle may be targets for this phosphatase.

We generated mice carrying a loss-of-function mutation in Brn-2, a gene encoding a nervous system specific POU transcription factor, by gene targeting in embryonic stem cells. In homozygous mutant embryos, migratory precursor cells for neurons of the paraventricular nuclei (PVN) and the supraoptic nuclei (SO) of the hypothalamus die at -E12.5. All homozygous mutants suffered mortality within 10 days after birth, possibly because of a complete deficiency of these neurons in the hypothalamus. Although neither developmental nor histological abnormalities were observed in heterozygous mice, the levels of expression of vasopressin and oxytocin in the hypothalamus of these animals were half these of wild-type mice. These results strongly suggest that Brn-2 plays an essential role in the determination and development of the PVN and SO neuronal lineages in the hypothalamus.

Prostaglandin (PG) D 2 is the most abundant prostanoid produced in the central nervous system of mammals and has been implicated in the modulation of neural functions such as sleep induction, nociception, regulation of body temperature, and odor responses. We generated geneknockout mice for lipocalin-type PGD 2 synthase (L-PGDS) and found that the intrathecal administration of PGE 2 , an endogenous pain-producing substance, failed to elicit allodynia (touch-evoked pain), which is one typical phenomenon of neuropathic pain, whereas it evoked thermal hyperalgesia, in L-PGDS؊͞؊ mice. We also found that the allodynic response induced by the ␥-aminobutyric acid (GABA) A receptor antagonist bicuculline was selectively abolished in the L-PGDS؊͞؊ mice, among excitatory and inhibitory agents that induced allodynia in wild-type mice. Interestingly, simultaneous injection of a femtogram amount of PGD 2 with PGE 2 or bicuculline induced allodynia in L-PGDS؊͞؊ mice to the same extent as in wild-type mice. The PGE 2 -or bicucullineevoked allodynia in wild-type and in PGD 2 -supplemented L-PGDS؊͞؊ mice was blocked by a PGD 2 receptor antagonist given in a femtogram amount. These results reveal that endogenous PGD 2 is essential for both PGE 2 -and bicucullineinduced allodynia.Prostaglandin (PG) D 2 is the major prostanoid produced in the central nervous system (CNS) of mammals (1, 2) and has been shown to be involved in a variety of central actions, e.g., it induces sleep, decreases body temperature, and modulates odor and pain responses (3-5). Among the three enzymes catalyzing the conversion of PGH 2 to PGD 2 (6, 7), lipocalintype PGD synthase (L-PGDS) is considered to be responsible for the biosynthesis of PGD 2 in the CNS. L-PGDS is present mainly in the leptomeninges, choroid plexus, and oligodendrocytes of the CNS (8, 9), and is secreted into the cerebrospinal fluid to become ␤-trace (10, 11), a major protein component of the cerebrospinal fluid (12-14). The receptor for PGD 2 , the D type of PG (DP) receptor (15, 16), also is localized in the leptomeninges of the brain (17, 18). Therefore, PGD 2 is assumed to be produced in the membranous tissues and oligodendrocytes of the CNS; to circulate through the cerebrospinal fluid in the ventricular system, subarachnoidal space, and extracellular space in the CNS; to interact with DP receptors in the meninges; and to act as a neurohormone or an informational substance for global regulation of various CNS functions (5).Prolonged tissue damage or injury often leads to chronic pain states such that noxious stimuli evoke hyperalgesia and innocuous tactile stimuli evoke pain (allodynia). In relation to clinically relevant hyperalgesic states, such as inflammation and neuropathic pain, there is considerable interest in the neurochemical mechanisms of hyperalgesia and allodynia (19-21). Since Vane (22) reported that aspirin-like drugs prevented the development of inflammation by blocking the synthesis of PGs, it has been widely accepted that PGs are involved in inflammation an...

The wee1+ gene is a mitotic inhibitor controlling the G2 to M transition of the fission yeast Schizosaccharomyces pombe and encodes a protein kinase with both serine- and tyrosine-phosphorylating activities. We have cloned a human gene (WEE1Hu) similar to wee1+ by transcomplementation of a yeast mutant. WEE1Hu encodes a protein homologous to the S. pombe wee1+ and mik1+ (a functionally redundant sibling of wee1+) kinases and effectively rescues a wee1 mutation. We report here that overexpression of WEE1Hu in fission yeast generates very elongated cells as a result of inhibition of the G2-M transition in the cell cycle. In addition, we detected a 3-kilobase-long WEE1Hu messenger RNA in all the human cell lines we examined. We conclude that a wee1(+)-like gene exists and is expressed in human cells.

Elongation factor-1 alpha (EF-1 alpha), an essential component of the eukaryotic translational apparatus, is a GTP-binding protein that catalyses the binding of aminoacyl-transfer RNAs to the ribosome. Expression of the EF-1 alpha gene decreases towards the end of the lifespans of mouse and human fibroblasts, but forced expression of EF-1 alpha prolongs the lifespan of Drosophila melanogaster. Eukaryotic initiation factor-4E, another component of the translational machinery, is mitogenic or oncogenic when constitutively expressed in some mammalian cells. Thus, components of the protein synthesis apparatus seem to be involved in the control of cell proliferation. Using expression cloning, we have isolated a complementary DNA clone from a BALB/c 3T3 mouse fibroblast variant, A31-I-13 (ref. 10), which specifies a factor determining the susceptibility of BALB/c3T3 to chemically and physically induced transformation. Here we report that the factor is EF-1 alpha and that its constitutive expression causes BALB/c 3T3 A31-I-1 (ref. 10), C3H10T1/2 (ref. 11) and Syrian hamster SHOK fibroblasts to become highly susceptible to transformation induced by 3-methylcholanthrene and ultraviolet light. EF-1 alpha messenger RNA is also constitutively expressed in a quiescent culture of the highly susceptible variant A31-I-13. We conclude that the removal of regulation of the expression of these components of the translational machinery may predispose cells to become more susceptible to malignant transformation.

The number of rRNA genes in Mycobacterium bovis BCG was examined by Southern hybridization of end-labeled 5S, 16S, and 23S rRNAs with BamHI, PstI, and Sall digests of M. bovis BCG DNA. Each RNA probe gave only one radioactive band with three kinds of DNA digest. These results suggest that M. bovis BCG chromosomes may carry only a minimum set of rRNA genes. Hybridization of randomly labeled rRNAs with BamHI, PstI, Sall, BgIlI, Hindlll, and PvuII digests of DNA from the same organism supported these conclusions. The 6.4-kilobase-pair SalI fragment containing the entire structural genes for both 16S and 23S rRNAs was cloned into pBR322. The cloned fragment was characterized by restriction endonuclease mapping, DNA-RNA hybridization analysis, and the R-loop technique. The results indicated that the fragments contained rRNA genes in the following order: 16S, 23S, and 5S rRNA genes. No tRNA gene was detected in the spacer region between the 16S and 23S rRNA genes, but one was found downstream of the 23S rRNA and 5S rRNA genes.We have been studying the molecular biology of Mycobacterium spp., with special emphasis on ribosomes. Our interest in rRNA genes was aroused because ribosomes of Mycobacterium smegmatis can not translate f2 RNA in a cell-free system. This defect in M. smegmatis ribosomes is thought to be due not only to a possible incompatibility of SI protein but perhaps also to more general differences in the structure of the ribosome (28). Thus, understanding the structure of mycobacterial ribosomes might be of great importance. Here we report the structure of genes for rRNAs in Mycobacterium bovis BCG.MATERIALS AND METHODS Chemicals. All restriction endonucleases and T4 DNA ligase were purchased from Toyobo Co. Ltd., Osaka, Japan. T4 polynucleotide kinase was from Takara Shuzo Co. Ltd., Osaka, Japan; T4 RNA ligase was from Pharmacia Japan, Tokyo, Japan; RNase A and yeast tRNAs were from Sigma Chemical Co., St. Louis, Mo. Both [-y-32P]ATP and [5'-32P]pCp were from Amersham Japan Co. Ltd., Tokyo, Japan.Bacterial strain and culture. M. bovis BCG ATCC 19274 was obtained from the American Type Culture Collection, Rockville, Md., and maintained in our laboratory. Cells were grown at 37°C in Sauton medium (asparagine, 4.0 g; citric acid, 2.0 g; sodium citrate, 2.8 g; potassium phosphate, 0.5 g; magnesium sulfate, 0.5 g; ammonium ferric citrate, 0.05 g; glycerol, 60 ml; distilled water, 1,000 ml).Preparation of rRNAs. Ribosomes and ribosomal subunits were prepared as described previously (29). Each rRNA species was obtained from 50S or 30S ribosomal subunits or from 70S ribosomes by the phenol extraction method (30), and was purified by two cycles of sucrose gradient centrifugation (10 to 30%). The SS and 4S RNAs were further purified by 10% polyacrylamide-7 M urea gel electrophoresis (21). Randomly labeled rRNAs. A 1-,ug amount of 16S and 23S rRNAs was partially hydrolyzed in 10 p.l of 0.1 M Tris hydrochloride (pH 9.7) at 90°C for 15 min to obtain fragments of about 100 base pairs (bp); these were recovered by etha...

The complete nucleotide sequence of the 16S rRNA gene of Mycobacterium bovis BCG was determined. Its coding region was estimated to be 1,536 base pairs long. The nucleotide sequence of the gene in M. bovis BCG has homologies of 75 and 89% with those of Escherichia coli and Streptomyces lividans, respectively.The special interest in the structure of the 16S rRNA from Mycobacterium bovis BCG arose from the finding that mycobacterial ribosome does not translate f2 bacteriophage RNA in a cell-free system (12). Since the 3' terminus of bacterial 16S rRNA has been implicated in the recognition of polypeptide chain initiation (6, 7), we analyzed the structure of 16S rRNA from M. bovis BCG. Southern hybridization analysis of rRNAs from M. bovis BCG was performed to determine the number of rRNA genes and the strategy for cloning. The results suggest that M. bovis BCG possesses only a minimum set of rRNA genes and that the spacer region between the genes for 16S and 23S rRNAs contains Institute for Fundamental Science, Ajinomoto Co. Ltd. (Kanagawa, Japan).The recombinant plasmid pBCG4 containing the entire rRNA operon of M. bovis BCG was propagated in Escherichia coli HB101 cells and isolated as described by Hughes and Meynell (1). The DNA was digested by BalI and separated by 1.0% agarose gel electrophoresis. The 1.7-kilobase-pair (kbp) DNA fragment was purified by using DE81 paper (10), cloned into the SmaI site of pUC18, and named pBCG1O1. The 1.0-kbp BamHI fragment was also cloned into the BamHI site of pUC18 and named pBCG102.Various restriction fragments were cut out from pBCG101 no tRNA genes (10). This paper describes the complete nucleotide sequence of the 16S rRNA gene and the spacer region between the 16S and 23S rRNA genes. All the restriction enzymes, T4 ligase, and T4 polynucleotide kinase were purchased from Toyobo Co. Ltd. (Tokyo, Japan); T4 RNA ligase was from Pharmacia Japan Co. Ltd. (Tokyo); phage M13 DNA, the 17-mer primer, and the deaza-DNA sequencing kit were from Takara Shuzo Co.

In mammalian cells, p34 cdc2 kinase undergoes phosphorylation at threonine‐14, tyrosine‐15 and threonine‐161 in the S and G2 phases of the cell cycle. At the onset of mitosis, the kinase becomes dephosphorylated at threonine‐14 and tyrosine‐15, resulting in activation. Cdc25 phosphatase has been shown to dephosphorylate tyrosine‐15 in vitro, but whether it also does at threonine‐14 remains unclear. In this study, we have found that human cdc25B phosphatase dephosphorylates both threonine‐14 and tyrosine‐15 but not threonine‐161.