Transformation of cell adhesion properties by exogenously introduced E-cadherin cDNA

E-cadherin is a cell surface glycoprotein responsible for Ca2+-dependent intercellular adhesion between epithelial cells; it is also called uvomorulin, L-CAM (ref. 3), cell-CAM 120/80 (ref.4) or Arc-1 (ref. 5). Because blocking the action of E-cadherin by monoclonal antibodies causes dispersion of compact cell colonies, this molecule is thought to be an important factor for maintenance of multicellular systems. To demonstrate directly that E-cadherin is involved in cell-cell adhesion, we cloned full-length cDNA encoding E-cadherin from F9 cells and introduced it into L fibroblasts deficient in E-cadherin. These L cells acquire strong Ca2+-dependent aggregating activity by expressing the E-cadherin derived from the introduced cDNA and were morphologically transformed so as to form colonies in which cells were tightly connected to each other.

Standard steroid treatment for autoimmune pancreatitis

OBJECTIVE

To establish an appropriate steroid treatment regimen for autoimmune pancreatitis (AIP).

METHODS

A retrospective survey of AIP treatment was conducted in 17 centres in Japan. The main outcome measures were rate of remission and relapse.

RESULTS

Of 563 patients with AIP, 459 (82%) received steroid treatment. The remission rate of steroid-treated AIP was 98%, which was significantly higher than that of patients without steroid treatment (74%, 77/104; p<0.001). Steroid treatment was given for obstructive jaundice (60%), abdominal pain (11%), associated extrapancreatic lesions except the biliary duct (11%), and diffuse enlargement of the pancreas (10%). There was no relationship between the period necessary to achieve remission and the initial dose (30 mg/day vs 40 mg/day) of prednisolone. Maintenance steroid treatment was given in 377 (82%) of 459 steroid-treated patients, and steroid treatment was stopped in 104 patients. The relapse rate of patients with AIP on maintenance treatment was 23% (63/273), which was significantly lower than that of patients who stopped maintenance treatment (34%, 35/104; p = 0.048). From the start of steroid treatment, 56% (55/99) relapsed within 1 year and 92% (91/99) relapsed within 3 years. Of the 89 relapsed patients, 83 (93%) received steroid re-treatment, and steroid re-treatment was effective in 97% of them.

CONCLUSIONS

The major indication for steroid treatment in AIP is the presence of symptoms. An initial prednisolone dose of 0.6 mg/kg/day, is recommend, which is then reduced to a maintenance dose over a period of 3-6 months. Maintenance treatment with low-dose steroid reduces but dose not eliminate relapses.

Autoimmune-related pancreatitis is associated with autoantibodies and a Th1/Th2-type cellular immune response

BACKGROUND & AIMS

Although autoimmunity may be involved in some cases of pancreatitis, the mechanism is still unknown. To clarify this, we studied serum autoantibodies, subsets of lymphocytes, and the Th1/Th2 balance of cellular immune responses in patients with autoimmune-related pancreatitis (AIP).

METHODS

Seventeen patients with AIP (8 men and 9 women; age, 53.2 +/- 13.0 years) were studied. Autoantibodies including antilactoferrin (ALF) or carbonic anhydrase II antibody (ACA-II) were examined using the enzyme-linked immunosorbent assay (ELISA) or the indirect fluorescein antibody method. Intracellular cytokines (interferon gamma and interleukin 4) and subtypes of peripheral blood lymphocytes were examined by flow cytometry and ELISA.

RESULTS

More than one autoantibody was observed in all 17 patients. Serum antinuclear antibody was detected in 13 of 17 patients, ALF antibody in 13, ACA-II antibody in 10, rheumatoid factor in 5, and anti-smooth muscle antibody in 3, but antimitochondrial antibody in none. The serum levels of ACA-II and LF antibody were not correlated. HLA-DR(+)CD8(+) and HLA-DR(+)CD4(+) cells were significantly increased in peripheral blood (P < 0.05). CD4(+) cells producing interferon gamma and the secreted levels were significantly increased compared with those in controls (P < 0.05), but interleukin 4 was not increased.

CONCLUSIONS

An autoimmune mechanism against CA-II or LF, and Th1-type immune response, may be involved in AIP.

High-frequency transformation method and library transducing vectors for cloning mammalian cDNAs by trans-complementation of Schizosaccharomyces pombe

We describe a highly efficient alkali cation method and library transducing vectors for cloning mammalian cDNAs by trans-complementation of fission yeast Schizosaccharomyces pombe mutants. cDNA libraries constructed with the pcD or pcD2 vector are transduced into yeast by cotransfection with a linearized vector, which allows an enhanced homologous recombination between the yeast vector and the library plasmid leading to the efficient formation of concatemers containing pcD molecules. The transformation frequencies obtained by the method are 10(6) colonies per 10(8) cells transfected with 2 micrograms of library and 1 microgram of vector, 50-60% of which contain pcD molecules. The high-efficiency alkali cation method circumvents many of the shortcomings of the spheroplast method generally used for Schiz. pombe transfection. The vectors are maximized for the efficiency of library transduction and minimized for the rearrangements of pcD molecules during propagation in yeast. This system allows rapid screening of multi-million cDNA clone libraries for rare cDNAs in a routine scale of experiments. Using this system, various mammalian cDNAs that are extremely difficult, time-consuming, or unclonable to clone by other methods have been cloned.

Parthenogenetic activation of oocytes in c-mos-deficient mice

In Xenopus the c-mos proto-oncogene product (Mos) is essential for the initiation of oocyte maturation, for the progression from meiosis I to meiosis II and for the second meiotic metaphase arrest, acting as an essential component of the cytostatic factor CSF. Its function in mouse oocytes is unclear, however, as is the biological significance of c-mos mRNA expression in testes and several somatic tissues. We have generated c-mos-deficient mice by gene targeting in embryonic stem cells. These mice grew at the same rate as their wild-type counterparts and reproduction was normal in the males, but the fertility of the females was very low. The c-mos-deficient female mice developed ovarian teratomas at a high frequency. Oocytes from these females matured to the second meiotic metaphase both in vivo and in vitro, but were activated without fertilization. The results indicate that in mice Mos plays a role in the second meiotic metaphase arrest, but does not seem to be essential for the initiation of oocyte maturation, spermatogenesis or somatic cell cycle.

Autoimmune related pancreatitis

Since the first documented case of a particular form of pancreatitis with hypergammaglobulinaemia, similar cases have been reported, leading to the concept of an autoimmune related pancreatitis or so-called "autoimmune pancreatitis". Although it has not yet been widely accepted as a new clinical entity, the present article discusses the recent concept of autoimmune pancreatitis.

Oxindole derivatives as orally active potent growth hormone secretagogues

A series of substituted oxindole derivatives was synthesized and evaluated for growth hormone (GH) releasing activity using cultured rat pituitary cells. (+)-6-Carbamoyl-3-(2-chlorophenyl)-(2-diethylaminoethyl)-4-trifluoromethyloxindole (SM-130686, 37S) was found to have potent activity (EC(50) = 3.0 nM), while the other enantiomer 37R had reduced activity. The absolute configuration of 37S was confirmed by X-ray crystallographic analysis. Compound 37S showed a good pharmacokinetic profile in rats with 28% oral bioavailability at 10 mg/kg and excellent in vivo activity as evidenced by a significant weight gain after 4 days of oral administration at 10 mg/kg twice a day. Compound 37S displaced the binding of (35)S-MK-677 to human GHS-R with an IC(50) value of 1.2 +/- 0.2 nM.

Serous cystic neoplasm of the pancreas: a multinational study of 2622 patients under the auspices of the International Association of Pancreatology and European Pancreatic Club (European Study Group on Cystic Tumors of the Pancreas)

OBJECTIVES

Serous cystic neoplasm (SCN) is a cystic neoplasm of the pancreas whose natural history is poorly known. The purpose of the study was to attempt to describe the natural history of SCN, including the specific mortality.

DESIGN

Retrospective multinational study including SCN diagnosed between 1990 and 2014.

RESULTS

2622 patients were included. Seventy-four per cent were women, and median age at diagnosis was 58 years (16-99). Patients presented with non-specific abdominal pain (27%), pancreaticobiliary symptoms (9%), diabetes mellitus (5%), other symptoms (4%) and/or were asymptomatic (61%). Fifty-two per cent of patients were operated on during the first year after diagnosis (median size: 40 mm (2-200)), 9% had resection beyond 1 year of follow-up (3 years (1-20), size at diagnosis: 25 mm (4-140)) and 39% had no surgery (3.6 years (1-23), 25.5 mm (1-200)). Surgical indications were (not exclusive) uncertain diagnosis (60%), symptoms (23%), size increase (12%), large size (6%) and adjacent organ compression (5%). In patients followed beyond 1 year (n=1271), size increased in 37% (growth rate: 4 mm/year), was stable in 57% and decreased in 6%. Three serous cystadenocarcinomas were recorded. Postoperative mortality was 0.6% (n=10), and SCN's related mortality was 0.1% (n=1).

CONCLUSIONS

After a 3-year follow-up, clinical relevant symptoms occurred in a very small proportion of patients and size slowly increased in less than half. Surgical treatment should be proposed only for diagnosis remaining uncertain after complete workup, significant and related symptoms or exceptionally when exists concern with malignancy. This study supports an initial conservative management in the majority of patients with SCN.

TRIAL REGISTRATION NUMBER

IRB 00006477.

Th1 but not Th17 cells predominate in the joints of patients with rheumatoid arthritis

OBJECTIVES

Recent animal studies have revealed critical roles of interleukin (IL)17, which is produced by a newly identified subset of helper T cells, Th17 cells, in the development of autoimmune diseases including arthritis. However, in human rheumatoid arthritis (RA), detailed characteristics and the prevalence of Th17 cells are unclear.

METHODS

Peripheral blood mononuclear cells (PBMC) were obtained from 123 patients with RA and 28 healthy controls. Mononuclear cells were also prepared from synovial membrane or synovial fluid of 12 patients with RA. IL17 (IL17A) positive T cells were identified by a flow cytometer after ex vivo stimulation with phorbol myristate acetate and ionomycin. Disease activity was assessed with the 28-joint Disease Activity Score (DAS28).

RESULTS

IL17 positive cells were detected in CD45RO+ CD4 T cells. Most IL17 positive T cells produced neither interferon (IFN)gamma nor IL4, but tumour necrosis factor (TNF)alpha similar to murine Th17 cells. The frequency of Th17 cells was neither increased in RA nor correlated with DAS28. Unexpectedly, the frequency of Th17 cells was significantly decreased in the joints compared with PBMC of the same patients with RA, whereas Th1 cells were more abundant in the joints than in PBMC.

CONCLUSIONS

We could not obtain evidence that positively supports predominance of Th17 cells in RA. Further careful investigation is necessary before clinical application of IL17-targeting therapy.

Two pairs of recombination signals are sufficient to cause immunoglobulin V-(D)-J joining

The minimum sequence requirements for antigen receptor V-(D)-J joining were studied by constructing recombination-substrates containing synthetic recombination signals and introducing them into a recombination-competent pre-B cell line. Two sets of heptamer (CACTGTG) and nonamer (GGTTTTTGT) sequences were shown to be sufficient to cause the V-(D)-J joining, if the 12- and 23-base pair spacer rule is satisfied. A point mutation in the heptamer sequence, or a change in the combination of the two spacer lengths, drastically reduced the recombination.

Suppression of DNA replication via Mos function during meiotic divisions in Xenopus oocytes

Meiosis is characterized by the absence of DNA replication between the two successive divisions. In Xenopus eggs, the ability to replicate DNA develops during meiotic maturation, but is normally suppressed until fertilization. Here we show that development of the DNA-replicating ability depends on new protein synthesis during meiosis I, and that mere ablation of the endogenous c-mos product Mos allows maturing oocytes to enter interphase and replicate DNA just after meiosis I. Moreover, we demonstrate that during normal maturation cdc2 kinase undergoes precocious inactivation in meiosis I and then premature reactivation before meiosis II; importantly, this premature cdc2 reactivation absolutely requires Mos function and its direct inhibition by a dominant-negative cdc2 mutant also results in nuclear reformation and DNA replication immediately after meiosis I. These findings indicate that suppression of DNA replication during meiotic divisions in Xenopus oocytes is accomplished by the Mos-mediated premature reactivation of cdc2 kinase. We suggest that these mechanisms for suppressing DNA replication may be specific for meiosis in animal oocytes, and that the ultimate biological function, including the well known cytostatic factor activity, of Mos during meiotic maturation may be to prevent undesirable DNA replication or parthenogenetic activation before fertilization.

The Mos/MAP kinase pathway stabilizes c-Fos by phosphorylation and augments its transforming activity in NIH 3T3 cells

The c-mos proto-oncogene product, Mos, is a serine/threonine kinase that can activate ERK1 and 2 mitogen-activated protein (MAP) kinases by direct phosphorylation of MAPK/ERK kinase (MEK). ERK activation is essential for oncogenic transformation of NIH 3T3 cells by Mos. In this study, we examined how mitogenic and oncogenic signalling from the Mos/MEK/ERK pathway reaches the nucleus to activate downstream target genes. We show that c-Fos (the c-fos protooncogene product), which is an intrinsically unstable nuclear protein, is metabolically highly stabilized, and greatly enhances the transforming efficiency of NIH 3T3 cells, by Mos. This stabilization of c-Fos required Mos-induced phosphorylation of its C-terminal region on Ser362 and Ser374, and double replacements of these serines with acidic (Asp) residues markedly increased the stability and transforming efficiency of c-Fos even in the absence of Mos. Moreover, activation of the ERK pathway was necessary and sufficient for the c-Fos phosphorylation and stabilization by Mos. These results indicate that c-Fos undergoes stabilization, and mediates at least partly the oncogenic signalling, by the Mos/MEK/ERK pathway. The present findings also suggest that, in general, the ERK pathway may regulate the cell fate and function by affecting the metabolic stability of c-Fos.

Perpetuation of influenza A viruses in Alaskan waterfowl reservoirs

To provide information on the mechanism of perpetuation of influenza viruses among waterfowl reservoirs in nature, virological surveillance was carried out in Alaska during their breeding season in summer from 1991 to 1994. Influenza viruses were isolated mainly from fecal samples of dabbling ducks in their nesting places in central Alaska. The numbers of subtypes of 108 influenza virus isolates were 1 H2N3, 37 H3N8, 55 H4N6, 1 H7N3, 1 H8N2, 1 H10N2, 11 H10N7, and H10N9. Influenza viruses were also isolated from water samples of the lakes where they nest. Even in September of 1994 when the most ducks had left for migration to south, viruses were still isolated from the lake water. Phylogenetic analysis of the NP genes of the representative isolates showed that they belong to the North American lineage of avian influenza viruses, suggesting that the majority of the waterfowls breeding in central Alaska migrate to North America and not to Asia. The present results support the notion that influenza viruses have been maintained in waterfowl population by water-borne transmission and revealed the mechanism of year-by-year perpetuation of the viruses in the lakes where they breed.

Vinexin: a novel vinculin-binding protein with multiple SH3 domains enhances actin cytoskeletal organization

Using the yeast two-hybrid system and an in vitro binding assay, we have identified a novel protein termed vinexin as a vinculin-binding protein. By Northern blotting, we identified two types of vinexin mRNA that were 3 and 2 kb in length. Screening for full-length cDNA clones and sequencing indicated that the two mRNA encode 82- and 37-kD polypeptides termed vinexin alpha and beta, respectively. Both forms of vinexin share a common carboxyl-terminal sequence containing three SH3 domains. The larger vinexin alpha contains an additional amino-terminal sequence. The interaction between vinexin and vinculin was mediated by two SH3 domains of vinexin and the proline-rich region of vinculin. When expressed, vinexin alpha and beta localized to focal adhesions in NIH 3T3 fibroblasts, and to cell-cell junctions in epithelial LLC-PK1 cells. Furthermore, expression of vinexin increased focal adhesion size. Vinexin alpha also promoted upregulation of actin stress fiber formation. In addition, cell lines stably expressing vinexin beta showed enhanced cell spreading on fibronectin. These data identify vinexin as a novel focal adhesion and cell- cell adhesion protein that binds via SH3 domains to the hinge region of vinculin, which can enhance actin cytoskeletal organization and cell spreading.

Effective "short" double-balloon enteroscope for diagnostic and therapeutic ERCP in patients with altered gastrointestinal anatomy: a large case series

BACKGROUND AND STUDY AIMS

Although endoscopic retrograde cholangiopancreatography (ERCP) is technically challenging in patients with altered gastrointestinal anatomy, a double-balloon enteroscope (DBE) permits examinations of a much longer segment of the small bowel than does a standard endoscope, and may be used to perform ERCP in such patients. Since only limited accessories are available for a conventional DBE, we performed ERCP with a "short" DBE, which has a 2.8-mm working channel and a 152-cm working length and for which conventional accessories are available, in patients with altered gastrointestinal anatomy, and evaluated this alternative technique.

PATIENTS AND METHODS

In 68 patients with a Roux-en-Y total gastrectomy (n = 36), Billroth II gastrectomy (n = 17), or pancreatoduodenectomy (n = 15), ERCP (103 procedures) was performed with a "short" DBE.

RESULTS

Deep insertion was successful in 100/103 procedures (97 %). Cholangiogram was successfully obtained in 98/100 procedures (98 %). Treatment was accomplished in all 98 procedures in which a cholangiogram was obtained (100 %). Therapeutic interventions including stone extraction (n = 47), nasobiliary drainage (n = 38), stent placement (n = 36), sphincterotomy (n = 31), choledochojejunostomy dilation (n = 29), tumor biopsy (n = 10), and naso-pancreatic duct drainage (n = 1) were performed successfully. Complications occurred in 5/103 procedures (5 %), all in patients with Roux-en-Y reconstruction.

CONCLUSIONS

Despite the relatively high rate of complications seen in patients with Roux-en-Y reconstruction, ERCP with a "short" DBE is effective in patients who have undergone bowel reconstruction.

Clinical analysis of autoimmune-related pancreatitis

OBJECTIVE

Several investigators have reported on autoimmune-related pancreatitis, but the clinical findings and pathophysiology still remain unclear. To clarify it, we analyzed eight patients with autoimmune pancreatitis.

METHODS

We evaluated clinical findings in eight patients (four men and four women) with autoimmune-related pancreatitis. Patients were aged 45-73 yr (mean, 57.5 yr). We examined blood chemistry and immunological studies, including autoantibodies against lactoferrin or carbonic anhydrase II, and compared ERCP images with clinical findings. In two patients, we studied the subset of lymphocytes infiltrating in the pancreas by immunohistochemistry and flow cytometry.

RESULTS

Four of eight patients had jaundice, two had renal dysfunction, two had abdominal pain, and two had back pain. Three patients were complicated with other autoimmune diseases. Three patients showed abnormal pancreatic exocrine function by an N-benzoyl-L-tyrosyl-para-aminobenzoic acid excretion test. Antinuclear antibody was detected in four of eight patients, antilactoferrin antibody in three of six, anticarbonic anhydrase II antibody in two of six, antismooth muscle antibody in two of seven, and rheumatoid factor in one of eight. All eight patients showed segmental stenosis of the main pancreatic duct by ERCP. Four patients showed stenosis of the common bile duct as well as the pancreatic duct. Microscopic findings showed infiltration of CD4-positive lymphocytes around the pancreatic duct, and HLA-DR was expressed on both CD4-positive cells and pancreatic duct cells. In two patients, stenosis of the pancreatic duct improved by prednisolone.

CONCLUSIONS

Autoimmune mechanism may be involved in some patients with idiopathic pancreatitis associated with hypergammaglobulinemia.

Characterization of a fission yeast SUMO-1 homologue, pmt3p, required for multiple nuclear events, including the control of telomere length and chromosome segregation

Unlike ubiquitin, the ubiquitin-like protein modifier SUMO-1 and its budding yeast homologue Smt3p have been shown to be more important for posttranslational protein modification than for protein degradation. Here we describe the identification of the SUMO-1 homologue of fission yeast, which we show to be required for a number of nuclear events including the control of telomere length and chromosome segregation. A disruption of the pmt3(+) gene, the Schizosaccharomyces pombe homologue of SMT3, was not lethal, but mutant cells carrying the disrupted gene grew more slowly. The pmt3Delta cells showed various phenotypes such as aberrant mitosis, sensitivity to various reagents, and high-frequency loss of minichromosomes. Interestingly, we found that pmt3(+) is required for telomere length maintenance. Loss of Pmt3p function caused a striking increase in telomere length. When Pmt3p synthesis was restored, the telomeres became gradually shorter. This is the first demonstration of involvement of one of the Smt3p/SUMO-1 family proteins in telomere length maintenance. Fusion of Pmt3p to green fluorescent protein (GFP) showed that Pmt3p was predominantly localized as intense spots in the nucleus. One of the spots was shown to correspond to the spindle pole body (SPB). During prometaphase- and metaphase, the bright GFP signals at the SPB disappeared. These observations suggest that Pmt3p is required for kinetochore and/or SPB functions involved in chromosome segregation. The multiple functions of Pmt3p described here suggest that several nuclear proteins are regulated by Pmt3p conjugation.

Downregulation of beta1 integrins by Ebola virus glycoprotein: implication for virus entry

Filoviruses, including Ebola virus, are cytotoxic. To investigate the role of the Ebola virus glycoprotein (GP) in this cytopathic effect, we transiently expressed the GP in human kidney 293T cells. Expression of wild-type GP, but not the secretory form of the molecule lacking a membrane anchor, induced rounding and detachment of the cells, as did a chimeric GP containing its ectodomain and influenza virus hemagglutinin transmembrane-cytoplasmic domain. These results indicate that the GP ectodomain and its anchorage to the membrane are required for GP-induced morphologic changes in host cells. Since cell rounding and detachment could be associated with reduced levels of cell adhesion molecules, we also studied the expression of integrins, which are major molecules for adhesion to extracellular matrices, and found that the beta1 integrin group is downregulated by the GP. This result was further extended by experiments in which anti-beta1 monoclonal antibodies or purified integrins inhibited the infectivity of vesicular stomatitis virus pseudotyped with the GP. We suggest that integrins, especially the beta1 group, might interact with the GP and perhaps be involved in Ebola virus entry into cells.

Serum antibodies to carbonic anhydrase I and II in patients with idiopathic chronic pancreatitis and Sjögren's syndrome

BACKGROUND & AIMS

Patients with idiopathic chronic pancreatitis and Sjögren's syndrome show immune responses against a 60-kilodalton protein isolated from human pancreas extracts. Monoclonal antibody SP3-1, raised against the 60-kilodalton protein, reacts with ductal cells in several exocrine organs and cross-reacts with human carbonic anhydrase II. The present study evaluated serum from patients with these diseases for antibodies to human carbonic anhydrase I and II.

METHODS

An enzyme-linked immunosorbent assay was used to quantify serum antibody against carbonic anhydrase I and II.

RESULTS

Serum antibodies against carbonic anhydrase I and II were detected in 7 and 11 of 33 patients with idiopathic chronic pancreatitis, respectively, and in 8 and 13 of 21 patients with Sjögren's syndrome, respectively. The positive prevalence rates of patients with antibodies of carbonic anhydrase II were significantly different among patients with idiopathic chronic pancreatitis and Sjögren's syndrome compared with normal patients (1 of 21). There were no significant differences in the prevalence rates of patients with alcoholic chronic pancreatitis (3 of 20), gallstone-related chronic pancreatitis (0 of 7), and primary biliary cirrhosis (1 of 11).

CONCLUSIONS

The results suggest that carbonic anhydrase II is one candidate target antigen recognized during the autoimmune pathophysiology observed in idiopathic chronic pancreatitis and Sjögren's syndrome.

The structure of calcyclin reveals a novel homodimeric fold for S100 Ca(2+)-binding proteins

The S100 calcium-binding proteins are implicated as effectors in calcium-mediated signal transduction pathways. The three-dimensional structure of the S100 protein calcyclin has been determined in solution in the apo state by NMR spectroscopy and a computational strategy that incorporates a systematic docking protocol. This structure reveals a symmetric homodimeric fold that is unique among calcium-binding proteins. Dimerization is mediated by hydrophobic contacts from several highly conserved residues, which suggests that the dimer fold identified for calcyclin will serve as a structural paradigm for the S100 subfamily of calcium-binding proteins.

Stress signal, mediated by a Hog1-like MAP kinase, controls sexual development in fission yeast

We identified the phh1+ gene that encodes a MAP kinase as the effector of Wis1 MAP kinase kinase in fission yeast, which is highly homologous with HOG1 of S. cerevisiae. Heterothalic phh1 dsiruptant is phenotypically indistinguishable from wis1 deletion mutant, both displaying the same extent of partial sterility and enhanced sensitivity to a variety of stress. In phh1 disruptant, nitrogen starvation-induced expression of ste11+, a key controller of sexual differentiation, is markedly diminished. Ectopic expression of ste11+ effectively restores fertility, but not stress resistance, to the phh1 disruptant. These data show that stress signal, mediated by a MAP kinase, is required for efficient start of sexual differentiation.

The extracellular signal-regulated kinase pathway phosphorylates AML1, an acute myeloid leukemia gene product, and potentially regulates its transactivation ability

AML1 (also called PEBP2alphaB, CBFA2, or CBFalpha2) is one of the most frequently disrupted genes in chromosome abnormalities seen in human leukemias. It has been reported that AML1 plays several pivotal roles in myeloid hematopoietic differentiation and other biological phenomena, probably through the transcriptional regulation of various relevant genes. Here, we investigated the mechanism of regulation of AML1 functions through signal transduction pathways. The results showed that AML1 is phosphorylated in vivo on two serine residues within the proline-, serine-, and threonine-rich region, with dependence on the activation of extracellular signal-regulated kinase (ERK) and with interleukin-3 stimulation in a hematopoietic cell line. These in vivo phosphorylation sites of AML1 were phosphorylated directly in vitro by ERK. Although differences between wild-type AML1 and phosphorylation site mutants in DNA-binding affinity were not observed, we have shown that ERK-dependent phosphorylation potentiates the transactivation ability of AML1. Furthermore the phosphorylation site mutations reduced the transforming capacity of AML1 in fibroblast cells. These data indicate that AML1 functions are potentially regulated by ERK, which is activated by cytokine and growth factor stimuli. This study provides some important clues for clarifying unidentified facets of the regulatory mechanism of AML1 function.