Recombinant cyclin B-Cdk1-Suc1 capable of multi-site mitotic phosphorylation in vitro

Cyclin-dependent kinase 1 (Cdk1) complexed with cyclin B phosphorylates multiple sites on hundreds of proteins during mitosis. However, it is not fully understood how multi-site mitotic phosphorylation by cyclin B-Cdk1 controls the structures and functions of individual substrates. Here we develop an easy-to-use protocol to express recombinant vertebrate cyclin B and Cdk1 in insect cells from a single baculovirus vector and to purify their complexes with excellent homogeneity. A series of in-vitro assays demonstrate that the recombinant cyclin B-Cdk1 can efficiently and specifically phosphorylate the SP and TP motifs in substrates. The addition of Suc1 (a Cks1 homolog in fission yeast) accelerates multi-site phosphorylation of an artificial substrate containing TP motifs. Importantly, we show that mitosis-specific multi-subunit and multi-site phosphorylation of the condensin I complex can be recapitulated in vitro using recombinant cyclin B-Cdk1-Suc1. The materials and protocols described here will pave the way for dissecting the biochemical basis of critical mitotic processes that accompany Cdk1-mediated large-scale phosphorylation.

Molecular dissection of condensin II-mediated chromosome assembly using in vitro assays

In vertebrates, condensin I and condensin II cooperate to assemble rod-shaped chromosomes during mitosis. Although the mechanism of action and regulation of condensin I have been studied extensively, our corresponding knowledge of condensin II remains very limited. By introducing recombinant condensin II complexes into Xenopus egg extracts, we dissect the roles of its individual subunits in chromosome assembly. We find that one of two HEAT subunits, CAP-D3, plays a crucial role in condensin II-mediated assembly of chromosome axes, whereas the other HEAT subunit, CAP-G2, has a very strong negative impact on this process. The structural maintenance of chromosomes ATPase and the basic amino acid clusters of the kleisin subunit CAP-H2 are essential for this process. Deletion of the C-terminal tail of CAP-D3 increases the ability of condensin II to assemble chromosomes and further exposes a hidden function of CAP-G2 in the lateral compaction of chromosomes. Taken together, our results uncover a multilayered regulatory mechanism unique to condensin II, and provide profound implications for the evolution of condensin II.

A loop extrusion-independent mechanism contributes to condensin I-mediated chromosome shaping

Condensin I is a five-subunit protein complex that is central to mitotic chromosome assembly in eukaryotic cells. Despite recent progress, its molecular mechanisms of action remain to be fully elucidated. By using Xenopus egg extracts as a functional assay, we find that condensin I complexes harboring mutations in its kleisin subunit CAP-H produce chromosomes with confined axes in the presence of topoisomerase IIα (topo IIα) and highly compact structures (termed “beans”) with condensin-positive central cores in its absence. The bean phenotype depends on the SMC ATPase cycle and can be reversed by subsequent addition of topo IIα. The HEAT repeat subunit CAP-D2, but not CAP-G, is essential for the bean formation. Notably, loop extrusion activities of the mutant complexes cannot explain the chromosomal defects they exhibit in Xenopus egg extracts, implying that a loop extrusion–independent mechanism contributes to condensin I–mediated chromosome assembly and shaping. We provide evidence that condensin–condensin interactions underlie these processes.

Cell cycle-specific loading of condensin I is regulated by the N-terminal tail of its kleisin subunit

Condensin I is a pentameric protein complex that plays an essential role in mitotic chromosome assembly in eukaryotic cells. Although it has been shown that condensin I loading is mitosis specific, it remains poorly understood how the robust cell cycle regulation of condensin I is achieved. Here, we set up a panel of in vitro assays to demonstrate that cell cycle-specific loading of condensin I is regulated by the N-terminal tail (N-tail) of its kleisin subunit CAP-H. Deletion of the N-tail accelerates condensin I loading and chromosome assembly in Xenopus egg mitotic extracts. Phosphorylation-deficient and phosphorylation-mimetic mutations in the CAP-H N-tail decelerate and accelerate condensin I loading, respectively. Remarkably, deletion of the N-tail enables condensin I to assemble mitotic chromosome-like structures even in interphase extracts. Together with other extract-free functional assays in vitro, our results uncover one of the multilayered mechanisms that ensure cell cycle-specific loading of condensin I onto chromosomes.

Two inhibitory systems and CKIs regulate cell cycle exit of mammalian cardiomyocytes after birth

Mammalian cardiomyocytes actively proliferate during embryonic stages, following which they exit their cell cycle after birth, and the exit is maintained. Previously, we showed that two inhibitory systems (the G1-phase inhibitory system: repression of cyclin D1 expression; the M-phase inhibitory system: inhibition of CDK1 activation) maintain the cell cycle exit of mouse adult cardiomyocytes. We also showed that two CDK inhibitors (CKIs), p21(Cip1) and p27(Kip1), regulate the cell cycle exit in a portion of postnatal cardiomyocytes. It remains unknown whether the two inhibitory systems are involved in the cell cycle exit of postnatal cardiomyocytes and whether p21(Cip1) and p27(Kip1) also inhibit entry to M-phase. Here, we showed that more than 40% of cardiomyocytes entered an additional cell cycle by induction of cyclin D1 expression at postnatal stages, but M-phase entry was inhibited in the majority of cardiomyocytes. Marked cell cycle progression and endoreplication were observed in cardiomyocytes of p21(Cip1) knockout mice at 4 weeks of age. In addition, tri- and tetranucleated cardiomyocytes increased significantly in p21(Cip1) knockout mice. These data showed that the G1-phase inhibitory system and two CKIs (p21(Cip1) and p27(Kip1)) inhibit entry to an additional cell cycle in postnatal cardiomyocytes, and that the M-phase inhibitory system and p21(Cip1) inhibit M-phase entry of cardiomyocytes which have entered the additional cell cycle.

Repression of cyclin D1 expression is necessary for the maintenance of cell cycle exit in adult mammalian cardiomyocytes

The hearts of neonatal mice and adult zebrafish can regenerate after injury through proliferation of preexisting cardiomyocytes. However, adult mammals are not capable of cardiac regeneration because almost all cardiomyocytes exit their cell cycle. Exactly how the cell cycle exit is maintained and how many adult cardiomyocytes have the potential to reenter the cell cycle are unknown. The expression and activation levels of main cyclin-cyclin-dependent kinase (CDK) complexes are extremely low or undetectable at adult stages. The nuclear DNA content of almost all cardiomyocytes is 2C, indicating the cell cycle exit from G1-phase. Here, we induced expression of cyclin D1, which regulates the progression of G1-phase, only in differentiated cardiomyocytes of adult mice. In these cardiomyocytes, S-phase marker-positive cardiomyocytes and the expression of main cyclins and CDKs increased remarkably, although cyclin B1-CDK1 activation was inhibited in an ATM/ATR-independent manner. The phosphorylation pattern of CDK1 and expression pattern of Cdc25 subtypes suggested that a deficiency in the increase in Cdc25 (a and -b), which is required for M-phase entry, inhibited the cyclin B1-CDK1 activation. Finally, analysis of cell cycle distribution patterns showed that >40% of adult mouse cardiomyocytes reentered the cell cycle by the induction of cyclin D1. The cell cycle of these binucleated cardiomyocytes was arrested before M-phase, and many mononucleated cardiomyocytes entered endoreplication. These data indicate that silencing the cyclin D1 expression is necessary for the maintenance of the cell cycle exit and suggest a mechanism that involves inhibition of M-phase entry.

CDK inhibitors, p21(Cip1) and p27(Kip1), participate in cell cycle exit of mammalian cardiomyocytes

Mammalian cardiomyocytes actively proliferate during embryonic stages, following which cardiomyocytes exit their cell cycle after birth. The irreversible cell cycle exit inhibits cardiac regeneration by the proliferation of pre-existing cardiomyocytes. Exactly how the cell cycle exit occurs remains largely unknown. Previously, we showed that cyclin E- and cyclin A-CDK activities are inhibited before the CDKs levels decrease in postnatal stages. This result suggests that factors such as CDK inhibitors (CKIs) inhibit CDK activities, and contribute to the cell cycle exit. In the present study, we focused on a Cip/Kip family, which can inhibit cyclin E- and cyclin A-CDK activities. Expression of p21(Cip1) and p27(Kip1) but not p57(Kip2) showed a peak around postnatal day 5, when cyclin E- and cyclin A-CDK activities start to decrease. p21(Cip1) and p27(Kip1) bound to cyclin E, cyclin A and CDK2 at postnatal stages. Cell cycle distribution patterns of postnatal cardiomyocytes in p21(Cip1) and p27(Kip1) knockout mice showed failure in the cell cycle exit at G1-phase, and endoreplication. These results indicate that p21(Cip1) and p27(Kip) play important roles in the cell cycle exit of postnatal cardiomyocytes.

Molecular genetic system for regenerative studies using newts

Urodele newts have the remarkable capability of organ regeneration, and have been used as a unique experimental model for more than a century. However, the mechanisms underlying regulation of the regeneration are not well understood, and gene functions in particular remain largely unknown. To elucidate gene function in regeneration, molecular genetic analyses are very powerful. In particular, it is important to establish transgenic or knockout (mutant) lines, and systematically cross these lines to study the functions of the genes. In fact, such systems have been developed for other vertebrate models. However, there is currently no experimental model system using molecular genetics for newt regenerative research due to difficulties with respect to breeding newts in the laboratory. Here, we show that the Iberian ribbed newt (Pleurodeles waltl) has outstanding properties as a laboratory newt. We developed conditions under which we can obtain a sufficient number and quality of eggs throughout the year, and shortened the period required for sexual maturation from 18 months to 6 months. In addition, P. waltl newts are known for their ability, like other newts, to regenerate various tissues. We revealed that their ability to regenerate various organs is equivalent to that of Japanese common newts. We also developed a method for efficient transgenesis. These studies demonstrate that P. waltl newts are a suitable model animal for analysis of regeneration using molecular genetics. Establishment of this experimental model will enable us to perform comparable studies using these newts and other vertebrate models.

Coordinated regulation of differentiation and proliferation of embryonic cardiomyocytes by a jumonji (Jarid2)-cyclin D1 pathway

In general, cell proliferation and differentiation show an inverse relationship, and are regulated in a coordinated manner during development. Embryonic cardiomyocytes must support embryonic life by functional differentiation such as beating, and proliferate actively to increase the size of the heart. Therefore, progression of both proliferation and differentiation is indispensable. It remains unknown whether proliferation and differentiation are related in these embryonic cardiomyocytes. We focused on abnormal phenotypes, such as hyperproliferation, inhibition of differentiation and enhanced expression of cyclin D1 in cardiomyocytes of mice with mutant jumonji (Jmj, Jarid2), which encodes the repressor of cyclin D1. Analysis of Jmj/cyclin D1 double mutant mice showed that Jmj was required for normal differentiation and normal expression of GATA4 protein through cyclin D1. Analysis of transgenic mice revealed that enhanced expression of cyclin D1 decreased GATA4 protein expression and inhibited the differentiation of cardiomyocytes in a CDK4/6-dependent manner, and that exogenous expression of GATA4 rescued the abnormal differentiation. Finally, CDK4 phosphorylated GATA4 directly, which promoted the degradation of GATA4 in cultured cells. These results suggest that CDK4 activated by cyclin D1 inhibits differentiation of cardiomyocytes by degradation of GATA4, and that initiation of Jmj expression unleashes the inhibition by repression of cyclin D1 expression and allows progression of differentiation, as well as repression of proliferation. Thus, a Jmj-cyclin D1 pathway coordinately regulates proliferation and differentiation of cardiomyocytes.

[Treatment of superior sulcus tumor]

We reported on 34 patients with superior sulcus non-small-cell lung cancer and clinical outcome. It is necessary to select the most appropriate approach from preoperative examination and the degree of infiltration at the chest wall. Recently, various approach and preoperative chemoradiotherapy followed by surgical resection is effective for the treatment of superior sulcus tumor (SST), we should keep challenging for radical resection in mind.

Cyclin A overexpression induces chromosomal double-strand breaks in mammalian cells

Cyclin A is a major regulator in vertebrate cell cycle, associated with cyclin-dependent kinase (Cdk), and involved in S-phase progression and entry into mitosis. It has been known that cyclin A overexpression not only causes premature S-phase entry but also induces prolongation of S phase. Here we show that ectopic expression of cyclin A leads to extensive gamma-H2AX focus formation, which is indicative of DNA double-strand breaks. Likewise, cyclin E, but not cyclin B1 and cyclin D1, also induced the gamma-H2AX focus formation, suggesting that these DNA lesions may be induced via aberrant DNA replication process. Moreover, the gamma-H2AX focus formation was suppressed by co-expressing p21(Cip1/Waf1) or dominant-negative Cdk2 mutant, suggesting that aberrant cyclin A-Cdk2 activation induces the chromosomal double-strand breaks.

Estimation of blood flow in the carotid artery and intraorbital ophthalmic artery by color pulse Doppler ultrasonography

Blood flow velocity was estimated in the orbital part of the ophthalmic artery and in the carotid artery, by way of pulse Doppler ultrasonography. The equipment was a Toshiba SSA-270A machine. The material comprised 12 glaucoma patients (20 eyes, all with open angles) under satisfactory IOP control, mean age 52 years, and 28 healthy controls (mean age 40 years; 54 eyes). Systolic flow velocities of 46 cm/sec and 103 cm/sec, in the ophthalmic and carotid artery respectively, were found in the normal subjects. With mean values of 42 and 116 cm/sec in the glaucoma group there was no significant difference between groups. The same applied to the average flow velocities. A considerable interindividual variation was found.

[Ultrasound biomicroscopic imaging diagnosis of the anterior segment of the eye with high-frequency ultrasonic diagnostic equipment]

Micro-imaging displays of the anterior segment of the eye, such as of the anterior chamber angle, iris, ciliary body, ciliary zonule of Zinn, and anterior surface of the crystalline lens, were obtained in human eyes in vivo by means of a recently developed, high-frequency, high-resolution ultrasonic diagnostic unit (30 MHz). Much clearer displays than conventional ultrasonic imaging displays (5-15 MHz) were obtained, showing improved resolution, and greater morphologic diagnostic information was provided. Displays considered useful for making measurements were also provided. The subjects were 20 normal volunteers (35 eyes), 36 patients with glaucoma (58 eyes), 6 patients with uveal diseases (6 eyes), and 28 patients with pseudophakia (32 eyes). The equipment used was a model UX-02 ultrasonic diagnostic unit (RION), and the transducer was the three-element annular array type. The frequency was 30 MHz, the resolution was below 50 microns, and tissue penetration was 6 mm. This method enabled close ultrasound biomicroscopic imaging observations of details of the anterior and posterior chambers of the eyes in vivo and was also useful for clinical diagnosis and elucidation of the cause of glaucoma of various types. It also for the first time enabled evaluation of the position of fixation of an intraocular lens loop in the pseudophakic eyes containing an intraocular lens.

[Evaluation of tissue plasminogen activator and plasminogen activator inhibitor-1 in blood obtained from patients of idiopathic central serous chorioretinopathy]

It is postulated that idiopathic central serous chorioretinopathy (ICSC) may be induced by a variety of underlying choroidal diseases capable of producing initially alterations in the permeability of the choriocapillaries. A history of unusual emotional stress frequently accompanies the onset of visual complaints. We have reported that alterations of serum lipids may exert a powerful effect on tissue plasminogen activator (t-PA) levels acting as a risk factor of variable cardioangiopathies. In this study, we evaluated the levels of t-PA activity, t-PA antigen and plasminogen activator inhibitor-1 (PAI-1) in blood from the patients with central serous chorioretinopathy, and compared them with the levels of total cholesterols (TCH), triglycerides (TG), and high-density lipoprotein cholesterol (HDL). t-PA activity levels and HDL were lower than in standard controls but t-PA antigen, PAI-1 antigen, and TG were higher. These facts may be associated with the pathogenesis or pathophysiological features of ICSC.

[Gross anatomical study of veins in the orbit]

The aim of this study is to clarify the major route of venous return in the orbit. Minute dissections were performed in 10 adult cadavers (5 males and 5 females) after being fixed in a 10% formalin solution. The superior ophthalmic vein (SOV) and its ascending anastomotic branch were consistently well-developed (the average maximum diameter: 6.2mm and 3.2mm, respectively) and these two veins formed the main venous channel from the orbital contents. The ascending anastomotic branch ran between the optic nerve and the medial rectus just behind the eyeball and joined the SOV. A large number of veins, including the inferior ophthalmic vein, which originated from the inferior contents of the orbit, drained into the ascending anastomotic branch. Arteries and/or nerves did not accompany their respective veins in the orbit, except for the lacrimal and ethmoidal veins. The posterior end of the SOV was severely narrowed lateral to the aponeurosis of the lateral rectus, while being conspicuously dilated just behind the eyeball. The above findings suggested that the dilated portion of SOV may act as a reservoir of the venous return of the orbit.

[Analysis of ocular circulatory kinetics in glaucoma by the ultrasonic Doppler method]

In order to analyze ocular circulatory kinetics in relation to the stages of progression of primary open-angle glaucoma, the pulse wave of flow velocity in the central retinal artery was measured by the ultrasonic Doppler method. In eyes with glaucoma, the ratio of blood flow velocity of the central retinal artery (fundus artery: FA) to that of the ophthalmic artery (medial frontal artery: OA) was smaller and, at the same time, the pulse rise time (PRT) of the pulse wave of flow velocity was shorter than in normal eyes, a tendency which increased as the disease progressed. The ratio of FA to OA in terms of velocity [V (FA/OA)] showed a significant inverse correlation with the degree of visual field disorder (Kosaki classification) and the ratio in terms of PRT [T (FA/OA)] showed significant inverse correlation with the C/D ratio of the papilla. An ultrasonic Doppler blood flowmeter with 2 frequencies, attached to an integral spectrum analyzer for indicating the direction of blood flow using real time sonography (Vasoflo-3), was used. The investigation was conducted on 100 eyes with primary open-angle glaucoma in 60 patients aged 20-70 years [28 males and 32 females (mean age 64.3 +/- 12.1)], and 60 eyes in 30 normal subjects of the same age (mean age 58.1 +/- 14.3). These results demonstrated that the ultrasonic Doppler method is useful for the observation of ocular circulatory kinetics in eyes with glaucoma.

Gastric carcinoma associated with dermatomyositis. Case report

A case of gastric carcinoma associated with dermatomyositis is reported. Total gastrectomy was performed and subsequently excision of hepatic metastasis. Although the cause-effect relationship between dermatomyositis and internal malignancy remains controversial, the obvious dependence of the clinical course of dermatomyositis on that of the gastric carcinoma in this case suggests a causal involvement.

[A case of remarkable regression of a colonic cancer involving metastasis to the liver as a result of FT-207 treatment]

In mid-August, 1986, a 50-year-old man underwent a detailed examination following the finding of a tumor in the upper abdominal region. The tumor was revealed to be a sigmoid colon cancer with multiple metastasis to both halves of the liver. Subsequent administration of FT-207 suppositories (750 mg X 2/day) resulted in a recognizable shrinkage of the metastatic lesions in the liver after one month, and a barium enema a month later indicated a decrease in the size of the original tumor. The pre-operative CEA value was 2,317 ng/ml, but this has reduced to 46.7 ng/ml to date March, 1987. In this report of single chemotherapy treatment with FT-207 of a sigmoid colon cancer involving metastasis to the liver, the prognosis obtained for the original and hepatic lesions has been good, and the patient's course to date healthy.

[Total parenteral nutrition and chemotherapy in cancer patients]

A common problem in cancer patients is a significant degree of malnutrition which disturbs and the accomplishment of surgery, chemotherapy and radiotherapy. Most patients with advanced cancer who should be treated with intensive chemotherapy are unable to ingest, digest or absorb sufficiently quantities of food and many antineoplastic agents affect the function of the alimentary tract. Therefore, total parenteral nutrition is a suitable method of nutritional support in these patients. The intravenous administration of nutrients can improve and maintain not only the nutritional status, but also the cell-mediated immunity of patients, and an effective or large doses of agents can be given as a result of increased tolerance. These effects are expected to enhance the potential of tumor response to chemotherapy. At the present time, only a few trials such as pulse TPN and amino acid imbalance therapy have been tried, but a specific nutritional regimen based on the altered metabolism in tumor and host should be developed in future.

[Comparison of continuous venous infusion of 5-FU and FT-207 under total parenteral nutrition]

Yoshida sarcoma-bearing rats were continuously infused with 5-FU at a dose of 20 mg/kg/day, and FT-207 at a dose of 40 mg/kg/day, 100 mg/kg/day or 140 mg/kg/day under TPN. After 4 days, rats were sacrificed and the 5-FU and FT-207 concentrations in their organs were measured. The 5-FU level in the tumor was almost the same at when 5-FU was injected at 20 mg/kg/day and FT-207 at 140 mg/kg/day. This 5-FU level in the tumor was twice and four times higher than that of the group injected with FT-207 at 100 mg/kg/day and 40 mg/kg/day. The 5-FU level in the tumor in all four groups was almost twice as high as that in the stomach, intestine and kidney, 7-10 times higher than that in the liver, and 10-30 times higher than that in serum. The FT-207 levels in the alimentary tract, kidney, tumor and serum were almost the same. The conclusion of our preliminary research is that FT-207 is recommended for use in continuous infusion at 7 times the dose of 5-FU when injected under TPN.

[Continuous venous infusion of 5-fluorouracil (5-FU) under total parenteral nutrition (TPN) in advanced gastric cancer]

Continuous venous infusion of 5-FU was investigated in patients with advanced gastric cancer under TPN. In preliminary research Yoshida Sarcoma-bearing rats were continuously infused with 5-FU at a dose of 20 mg/kg/day under TPN. The 5-FU level in the tumor was 2-5 times higher than that in the kidney, stomach, intestine and liver, and 40-50 times higher than that in serum. Advanced gastric cancer patients were continuously infused with 5-FU at a dose of 500 mg/day under TPN. Serum 5-FU level was constantly maintained at 0.05 mcg/ml during the infusion period. The effects of 5-FU continuously infused with other anticancer agents and TPN were satisfactory with regard to anticancer response and general condition. In conclusion, in advanced cancer, 5-FU is recommended for use in continuous infusion at a dose of 500 mg/day under TPN.

[The metabolic changes and nutritional management following radical surgery of esophageal cancer and total gastrectomy]

The metabolic changes after major surgery such as esophagectomy and total gastrectomy are remarkable. Postoperative levels of plasma catecholamines and glucagon were significantly higher in major surgery than those in the other operations (distal gastrectomy, cholecystectomy, mastectomy, etc). As the consequence of these hormonal changes, resting metabolic expenditure (RME) increased up to 30-40% above the predicted basal metabolic expenditure and blood glucose elevated to a high level. The relationships between RME, N-balance and energy intake after major surgery indicated that the intake of non-protein energy expenditure equal to RME was necessary in order to maintain N-balance. For the administration of enough energy after major surgery, TPN solution composed of glucose 180-240g, fructose 90-100g, xylitol 30-40g and amino acids 68-91g (the approximate weight ratio of G, F and X is 4: 2: 1) was developed since 1975 and in some cases, lipid solution was added as non-protein energy source. This solution was infused immediately after operation and no metabolic complications (hyper glycemia, acidosis, etc) were observed. This nutritional therapy has maintained the nutritional state of postoperative patients and improved our operative results. There are, however, many problems in the nutritional managements of the patients with severe complications and after the discharge of hospital. In the future, special nutritional therapy for these cases should be progressed.