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W Jiang

Publications and source records attributed to W Jiang.

At least 109 records · Page 6Linked to original sources
PubMed2000

Isolation and characterization of par1(+) and par2(+): two Schizosaccharomyces pombe genes encoding B' subunits of protein phosphatase 2A.

Protein phosphatase 2A (PP2A) is one of the major serine/threonine phosphatases found in eukaryotic cells. We cloned two genes, par1(+) and par2(+), encoding distinct B' subunits of PP2A in fission yeast. They share 52% identity at the amino acid sequence level. Neither gene is essential but together they are required for normal septum positioning and cytokinesis, for growth at both high and low temperature, and for growth under a number of stressful conditions. Immunofluorescence microscopy revealed that Par2p has a cell-cycle-related localization pattern, being localized at cell ends during interphase and forming a medial ring in cells that are undergoing septation and cytokinesis. Our analyses also indicate that Par1p is more abundant than Par2p in the cell. Cross-organism studies showed that both par1(+) and par2(+) could complement the rts1Delta allele in Saccharomyces cerevisiae, albeit to different extents, in spite of the fact that neither contains a serine/threonine-rich N-terminal domain like that found in the S. cerevisiae homolog Rts1p. Thus, while Schizosaccharomyces pombe is more similar to higher eukaryotes with respect to its complement of B'-encoding genes, the function of those proteins is conserved relative to that of Rts1p.

Amino Acid Sequence↗
PubMed2000

Analytical systematic approximate method of a two-state dissipative system

Occupation probability and changes of the environment in a dissipative two-state system have been investigated using a systematic approximate method. This method explores the tunneling dynamics through a system state vector with manifest physical meanings and provides a deep microscopic insight into the dynamical behaviors of the system.

Journal Article↗
PubMed2000

Genetic erosion in northern marginal population of the common wild rice Oryza rufipogon Griff. and its conservation, revealed by the change of population genetic structure.

In order to monitor genetic erosion within the northern marginal population of common wild rice Oryza rufipogon Griff. from Dongxiang, Jiangxi Province, China, allozyme diversity encoded by 22 loci was analyzed electrophoretically from all the existing subpopulations in 1980, 1985 and 1994. The sample collected from the nine large subpopulations in 1980 showed the highest levels of genetic diversity (A = 1.27, P = 18.20%, Ho = 0.042 and He = 0.049) and a slight deviation from Hardy-Weinberg expectation (F = 0.143), the sample from five moderate ones in 1985 displayed medium levels of genetic diversity (A = 1.14, P = 13.60%, Ho = 0.008 and He = 0.049) and a great deviation from Hardy-Weinberg expectation (F = 0.837), and the sample from two small ones in 1994 demonstrated the lowest levels of genetic diversity (A = 1.09, P = 9.10%, Ho = 0.000 and He = 0.043) and the largest deviation from Hardy-Weinberg expectation (F = 1.000). The results not only documented the genetic erosion stemmed from the extinction of the subpopulations, but also revealed the drastic change of the population genetic structure due to the reduction of the population. Finally, some conservation strategies for the population are proposed.

DNA, Plant↗
PubMed2000

Loss of a protein phosphatase 2A regulatory subunit (Cdc55p) elicits improper regulation of Swe1p degradation.

CDC55 encodes a Saccharomyces cerevisiae protein phosphatase 2A (PP2A) regulatory subunit. cdc55-null cells growing at low temperature exhibit a failure of cytokinesis and produce abnormally elongated buds, but cdc55-null cells producing the cyclin-dependent kinase Cdc28-Y19F, which is unable to be inhibited by Y19 phosphorylation, show a loss of the abnormal morphology. Furthermore, cdc55-null cells exhibit a hyperphosphorylation of Y19. For these reasons, we have examined in wild-type and cdc55-null cells the levels and activities of the kinase (Swe1p) and phosphatase (Mih1p) that normally regulate the extent of Cdc28 Y19 phosphorylation. We find that Mih1p levels are comparable in the two strains, and an estimate of the in vivo and in vitro phosphatase activity of this enzyme in the two cell types indicates no marked differences. By contrast, while Swe1p levels are similar in unsynchronized and S-phase-arrested wild-type and cdc55-null cells, Swe1 kinase is found at elevated levels in mitosis-arrested cdc55-null cells. This excess Swe1p in cdc55-null cells is the result of ectopic stabilization of this protein during G(2) and M, thereby accounting for the accumulation of Swe1p in mitosis-arrested cells. We also present evidence indicating that, in cdc55-null cells, misregulated PP2A phosphatase activity is the cause of both the ectopic stabilization of Swe1p and the production of the morphologically abnormal phenotype.

Alkaline Phosphatase↗
PubMed2000

Stretch and H reflexes in triceps surae are similar during tonic and rhythmic contractions in high decerebrate cats.

During locomotion in decerebrate and spinal cats the group Ia afferents from hind leg muscles are depolarized rhythmically. An earlier study concluded that this locomotor-related primary afferent depolarization (PAD) does not contribute to modulation of monosynaptic reflex pathways during locomotion. This finding indicated that the neural network generating the locomotor rhythm, the central pattern generator (CPG), does not presynaptically inhibit monosynaptic reflexes. In this investigation we tested this prediction in decerebrate cats by measuring the magnitude of reflexes evoked in ankle extensor muscles during periods of tonic contractions and during sequences of rhythmic contractions. The latter occurred when the animal was induced to walk on a treadmill. At the similar levels of activity in the soleus muscle there was no significant difference in the magnitude of the soleus H reflex in these two behavioral situations. Similar results were obtained for reflexes evoked by brief stretches of the soleus muscle. We also examined the reflexes evoked by ramp-and-hold stretches during periods of rhythmic and tonic activity of the isolated medial gastrocnemius (MG) muscle. At similar levels of background activity, the reflexes evoked in the MG muscle were the same during rhythmic and tonic contractions. Our failure to observe a reduction in the magnitude of H reflexes and stretch reflexes during rhythmic contractions, compared with reflexes evoked at the same level of background activity during tonic contractions, is consistent with the notion that the CPG for stepping does not presynaptically inhibit monosynaptic reflexes during the extension phase of locomotor activity. Our results indicate that presynaptic inhibition of the monosynaptic reflex associated with normal locomotion in cats or humans arises from sources other than the extensor burst generating system of the central pattern generator.

Animals↗
PubMed2000

The VC dimension for mixtures of binary classifiers.

The mixtures-of-experts (ME) methodology provides a tool of classification when experts of logistic regression models or Bernoulli models are mixed according to a set of local weights. We show that the Vapnik-Chervonenkis dimension of the ME architecture is bounded below by the number of experts m and above by O(m4s2), where s is the dimension of the input. For mixtures of Bernoulli experts with a scalar input, we show that the lower bound m is attained, in which case we obtain the exact result that the VC dimension is equal to the number of experts.

Expert Systems↗
PubMed2000

Coupling H(+) transport to rotary catalysis in F-type ATP synthases: structure and organization of the transmembrane rotary motor.

H(+)-transporting F(1)F(o)-type ATP synthases utilize a transmembrane H(+) potential to drive ATP formation by a rotary catalytic mechanism. ATP is formed in alternating beta subunits of the extramembranous F(1) sector of the enzyme, synthesis being driven by rotation of the gamma subunit in the center of the F(1) molecule between the alternating catalytic sites. The H(+) electrochemical potential is thought to drive gamma subunit rotation by first coupling H(+) transport to rotation of an oligomeric rotor of c subunits within the transmembrane F(o) sector. The gamma subunit is forced to turn with the c(12) oligomeric rotor as a result of connections between subunit c and the gamma and epsilon subunits of F(1). In this essay, we will review recent studies on the Escherichia coli F(o) sector. The monomeric structure of subunit c, determined by nuclear magnetic resonance (NMR), is discussed first and used as a basis for the rest of the review. A model for the structural organization of the c(12) oligomer in F(o), deduced from extensive cross-linking studies and by molecular modeling, is then described. The interactions between the the a(1)b(2) 'stator' subcomplex of F(o) and the c(12) oligomer are then considered. A functional interaction between transmembrane helix 4 of subunit a (aTMH-4) and transmembrane helix 2 of subunit c (cTMH-2) during the proton-release step from Asp61 on cTMH-2 is suggested. Current a-c cross-linking data can only be explained by helix-helix swiveling or rotation during the proton transfer steps. A model that mechanically links helix rotation within a single subunit c to the incremental 30 degrees rotation of the c(12) oligomer is proposed. In the final section, the structural interactions between the surface residues of the c(12) oligomer and subunits epsilon and gamma are considered. A molecular model for the binding of subunit epsilon between the exposed, polar surfaces of two subunits c in the oligomer is proposed on the basis of cross-linking data and the NMR structures of the individual subunits.

Binding Sites↗
PubMed2000

[DNA polymorphism of Pvu II site in the lipoprotein lipase gene in patients with type 2 diabetes mellitus].

OBJECTIVE: To study the relationship between the lipoprotein lipase(LPL) gene and type 2 diabetes mellitus (DM) and its lipid metabolism. METHODS: PCR-RFLP method was used to determine the DNA polymorphism of 6th intron at LPL gene in 127 DM patients and 125 controls. RESULTS: The allele frequencies in case and control groups were 69.3%, 63.6% for "P+" and 30.7%, 36.4% for "P-", respectively; the frequencies of genotypes were 48.0%, 44.8% for P+/P+, 42.5%, 37. 6% for P+/P- and 9.45%, 17.6% for P-/P-, respectively. There was no significant difference in frequencies of genotypes or alleles between the two groups. The LPL Pvu II polymorphism in Chinese population was similar to that in Japanese population, and was different from that in European and American population. CONCLUSION: The LPL-Pvu II-RFLP in Chinese population is not significantly associated with type 2 diabetes mellitus. The significant difference of Pvu II-RFLP among various races was observed.

Adult↗
PubMed2000

Co-transfection of MRP and bcl-2 antisense S-oligodeoxynucleotides reduces drug resistance in cisplatin-resistant lung cancer cells.

OBJECTIVE: To detect the influence of antisense s-oligodeoxynucleotides (S-ODNs) of bd-2 and multidrug resistance-associated protein (MRP) genes multidrug resistance-associated protein gene and bcl-2 antisense S-oligodeoxynucleotides on cisplatin-resistant lung adenocarcinoma cell line A549DDP which overexpresses both bcl-2 and MRP. METHODS: A549DDP cells were treated with sense and antisense S-ODN mediated by lipofection. Expression of MRP and bcl-2 mRNA and protein in the treated cells was measured by RT-PCR and flow cytometry (FCM), respectively. Apoptosis was identified by DNA electrophoresis and terminal deoxynucleotidyl transferase (TdT)-mediated biotin dUTP nick end-labeling (TUNEL). The degree of drug resistance of the treated cells was detected by a cell viability 3'-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyl-tefrazolium bromide thiazolylblue (MTT) assay. RESULTS: Expression of bcl-2 and MRP significantly decreased in the cells treated with bcl-2 or/and MRP antisense S-ODN for 48 h as compared to the cells untreated and sense-treated (P < 0.05). Resistance to cisplatin in the cells treated with bcl-2 or/and MRP antisense S-ODN decreased by 60.6% (6.5 times), 56.4% (7.2 times) and 71.0% (4.8 times), respectively, which paralleled the decrease of bcl-2 and MRP expression. Similarly, the resistance to etoposide and epirubicin in antisense-treated cells also reduced in parallel to decreases of the two gene expressions. The drug resistance in sense-treated cells was similar to that in untreated cells. Statistically significant dose- and concentration-dependent increases of apoptotic cells were observed in the groups exposed to 100 mumol/L cisplatin for 48 h after treatment by bcl-2 or/and MRP antisense. CONCLUSION: Bcl-2 and MRP were at least additive and possibly synergistic in conferring drug resistance in a cisplatin-resistant lung adenocarcinoma cell line. Antisense S-ODN could attenuate drug resistance by promoting cells apoptosis, which might lead to a new treatment for patients with non-small cell lung cancers (NSCLCs) who are refractory to conventional chemotherapy.

Adenocarcinoma↗
PubMed2000

Electrical remodeling of membrane ionic channels of hypertrophied ventricular myocytes from spontaneously hypertensive rats.

OBJECTIVE: To study the difference in membrane ionic currents between hypertrophied and normal myocytes and to explore the electrical remodeling of hypertrophied myocytes. METHODS: Membrane ionic channels were studied in enzymatically dispersed spontaneously hypertensive rats (SHRs) left ventricular myocytes using the whole-cell configuration of patch-clamp technique, with normal Wistar rats ventricular myocytes as controls. We observed depolarizing currents (sodium current, INa; L-type calcium current, L-ICa) and repolarizing currents (inward rectifier potassium current, IK1; delayed rectifier potassium current, IK; transient outward potassium current, Ito) and compared the differences between normal and hypertrophied myocytes. RESULTS: The heart to body weight ratio of Wistar rats and SHRs was 3.70 +/- 0.29 mg/g and 5.66 +/- 0.46 mg/g, respectively (P < 0.001), and the mean cell membrane capacitances were 189.94 +/- 56.59 pF and 280.68 +/- 67.98 pF, respectively (P < 0.05). These differences suggest that SHRs have heart hypertrophy and hypertrophied myocytes. The amplitude of L-Ica of SHRs (1944 +/- 466.8 pA) was significantly greater than that of Wistar rats (1136 +/- 383.3 pA) (P < 0.001), and the current density was 6.93 +/- 1.71 pA/pF and 6.19 +/- 2.85 pA/pF respectively when normalized to cell capacitance, and the slow inactivation time constant of SHRs was significantly prolonged (56.01 +/- 13.36 ms vs 43.63 +/- 17.89 ms, P < 0.001). The amplitude of INa of SHRs (6132.5 +/- 1162.9 pA) was significantly greater than that of Wistar rats (3613.9 +/- 794.44 pA) (P < 0.001), but there was no difference when normalized to cell capacitance (24.61 +/- 6.72 pA/pF vs 24.95 +/- 6.99 pA/pF). Channel activation and inactivation time constants were also the same. The amplitude of IK of SHRs (3461.5 +/- 1967.10 pA) was greater than that of Wistar rats (2302.4 +/- 893.72 pA) (P < 0.05), but there was no difference when normalized to cell capacitance (12.38 +/- 5.46 pA/pF vs 11.86 +/- 3.59 pA/pF). The inward portion of IK1 of SHRs was significantly lower than that of Wistar rats (11.3 +/- 2.26 pA/pF vs 14.3 +/- 3.00 pA/pF, P < 0.05), but there was no difference in the outward portion (2.360 +/- 0.86 pA/pF vs 2.957 +/- 1.27 pA/pF). The current density of Ito of SHRs (8.21 +/- 6.64 pA/pF) was significantly lower than that of Wistar rats (19.16 +/- 6.17 pA/pF) (P < 0.001), but channel kinetics were similar, suggesting that the reduction of Ito may result from the decrease in channel number. CONCLUSIONS: Membrane ionic current changes of hypertrophied left ventricular myocytes in SHRs include: 1. there was an increase of L-Ica, INa and Ik, but the current density was similar to that in normal myocytes, indicating that channel numbers increase as the myocytes become hypertrophied; 2. Ito was small in hypertrophied ventricular myocytes and its current density was even smaller, indicating that channel numbers decrease as the myocytes enlarge. The former is recognized as a physiologically compensatory change which does not lead to electrophysiological disturbance; the latter is viewed as pathological change, where the reduction of Ito may lead to a repolarizing delay in myocytes, prolongation of the action potential and the occurrence of arrhythmias because of repolarizing heterogeneity. Therefore, the reduction of Ito in hypertrophied myocytes should be recognized as a significant or substantial change of electrical remodeling.

Animals↗
PubMed2000

Telomerase activity and expression of the telomerase catalytic subunit gene in non-small cell lung cancer: correlation with decreased apoptosis and clinical prognosis.

OBJECTIVE: To investigate the level of telomerase activation (TA) and telomerase catalytic subunit (hEST2) gene mRNA in patients with non-small cell lung cancer, and determine whether they are associated with tumor cell apoptosis, stage, and clinical outcome. METHODS: Primary tumor specimens from 58 patients untreated with chemotherapy and 10 cases of histologically benign and adjacent lung tissue were analyzed. TA and hEST2 were measured by means of a modified telomerase repeat amplification protocol (TRAP) assay and in situ hybridization (ISH), respectively. Terminal deoxynucleotidyl transferase (TdT)-mediated biotin dUTP nick end-labeling (TUNEL) was used to evaluate apoptotic cells. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect bcl-2 mRNA expression. RESULTS: TA and hEST2 were detected in 45 (77.6%) and 43 (74.1%) of 58 tumor specimens, respectively, and not detected in specimens of adjacent and benign lung tissue. One case expressed hEST2 as a weak positive. Statistically significant positive association was found between the level of TA and hEST2 (r = 0.85, P = 0.001). TA and hEST2 were associated with tumor stage, but not associated with tumor grade, gender and patient age. Positive rate of bcl-2 mRNA was 38 (65.5%) of 58 tumor specimens. The mean apoptotic index in the bcl-2 positive group (9.5 +/- 1.3) was lower than that in the bcl-2 negative one (19.8 +/- 2.1, P < 0.05), suggesting that apoptotic index may be inversely associated with bcl-2 expression (r = -0.48, P = 0.041). Bcl-2 expression in the TA and hEST2 positive group (92.1% and 89.4%) was higher than that in the negative one (50.0% and 45.0%, P = 0.043 and P = 0.032, respectively). The apoptotic index was lower in the TA or hEST2 positive group (8.2 +/- 1.4, 10.7 +/- 1.1) than in the negative one (20.5 +/- 1.6, 24.2 +/- 2.1, P < 0.05). A statistically significant inverse association was found between TA or hEST2 and apoptotic index (r = -0.45, P = 0.02 and r = -0.51, P = 0.001, respectively). Positive correlation was also detected between TA or hEST2 and bcl-2 expression (r = 0.86, P = 0.01 and r = 0.73, P = 0.024, respectively). The level of hEST2 mRNA and apoptotic index were associated with clinical outcome in a multivariate cox regression analysis. CONCLUSIONS: High TA and hEST2 were frequently detected in primary non-small cell lung cancer untreated with chemotherapy, having high bcl-2 expression and a low tumor cell apoptotic rate. This suggests that both TA and hEST2 are correlated with the deregulation of apoptosis. hEST2 and apoptotic index have prognostic significance in patients with non-small cell lung cancer.

Adolescent↗
PubMed2000

[Expression of LRP, MRP and MDR1 in non-small-cell lung cancer and its clinical significance].

OBJECTIVE: To detect expression of lung resistance protein (LRP), multidrug resistance-associated protein(MRP) and multidrug resistance 1(MDR1) mRNA, and its clinical significance in non-small-cell lung cancer (NSCLC). METHODS: RT-PCR was used to investigate mRNA expression of the above mentioned genes. RESULTS: The frequency of expression of LRP, MRP and MDR1 was 74.2%, 80.3% and 37.9%, respectively. A significant positive correlation was observed between LRP and MRP(r = 0.47, P = 0.001), but this association was found neither between LRP and MDR1, nor between MRP and MDR1. The expression of LRP, MRP and MDR1 did not vary with the grade of cell differentiation and TNM staging. In adenocarcinomas which responded to chemotherapy, there was lowered expression of both LRP and MRP than those which did not respond. In chemo-responsive squamous-cell carcinomas, however, this was true of LRP expression only. The median survival time of NSCLC patients with co-expressed 2 and 3 drug resistance related genes was significantly reduced. CONCLUSION: The intrinsic multidrug resistance of NSCLC involves the combined effects of LRP, MRP and MDR1.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

[Clinical study on zhenjian granule in improving essential hypertension and insulin resistance].

OBJECTIVE: To observe the effect of Zhenjian granule (ZJG) on lowering the blood pressure and improving the essential hypertension (EH) and insulin resistance (IR). METHODS: Fifty-two hypertensive patients were randomly divided into the treated group (30 patients) with ZJG and the control group (22 patients) with captopril for 4 weeks, then the variation of levels of blood pressure, blood glucose, blood insulin (radioimmunoassay), insulin sensitivity index (ISI) and blood lipid before and after treatment were determined, and compared with the normal group (17 healthy subjects). RESULTS: Fasting insulin, blood glucose and insulin 2 hours after meal were significantly higher than those of the normal control, but the ISI was significantly lower than that of the normal control (P < 0.01), the insulin resistance existed; after treatment, not only the blood pressure obviously lowered (P < 0.05, P < 0.01), and the fasting insulin, blood glucose and insulin 2 hours after meal obviously lowered (P < 0.05, P < 0.01), ISI markedly raised (P < 0.05, P < 0.01). The IR of both groups was improved, the blood lipid of the treated group was also improved. CONCLUSION: ZJG was effective in reducing blood pressure, it also had significant effect on improving metabolic disorder, particularly on IR in EH patients.

Adult↗
PubMed1999

Overexpression of thioredoxin h leads to enhanced activity of starch debranching enzyme (pullulanase) in barley grain.

Biochemically active wheat thioredoxin h has been overexpressed in the endosperm of transgenic barley grain. Two DNA constructs containing the wheat thioredoxin h gene (wtrxh) were used for transformation; each contained wtrxh fused to an endosperm-specific B(1)-hordein promoter either with or without a signal peptide sequence for targeting to the protein body. Twenty-two stable, independently transformed regenerable lines were obtained by selecting with the herbicide bialaphos to test for the presence of the bar herbicide resistance gene on a cotransformed plasmid; all were positive for this gene. The presence of wtrxh was confirmed in 20 lines by PCR analysis, and the identity and level of expression of wheat thioredoxin h was assessed by immunoblots. Although levels varied among the different transgenic events, wheat thioredoxin h was consistently highly expressed (up to 30-fold) in the transgenic grain. Transgenic lines transformed with the B(1)-hordein promoter with a signal peptide sequence produced a higher level of wheat thioredoxin h on average than those without a signal sequence. The overexpression of thioredoxin h in the endosperm of germinated grain effected up to a 4-fold increase in the activity of the starch debranching enzyme, pullulanase (limit dextrinase), the enzyme that specifically cleaves alpha-1,6 linkages in starch. These results raise the question of how thioredoxin h enhances the activity of pullulanase because it was found that the inhibitor had become inactive before the enzyme showed appreciable activity.

Glycoside Hydrolases↗
PubMed1999

Structure of the carbonic anhydrase VI (CA6) gene: evidence for two distinct groups within the alpha-CA gene family.

The secreted carbonic anhydrase (CA VI) is believed to be one of the oldest mammalian CAs in evolutionary terms. To elucidate its gene structure and compare it with other members of the alpha-CA family, we cloned genomic fragments encoding the bovine CA6 gene and determined its exon/intron organization. The gene spans approx. 25 kb and consists of eight exons and seven introns. Exon 1 encodes the 5' untranslated region, the signal peptide and the N-terminus of the mature enzyme. Exon 8 encodes the 3' untranslated region and the C-terminal extension that is unique to CA VI. Exons 2-7 encode the CA domain, which shows significant sequence similarity to other CAs. Two distinct groups exist in the alpha-CA family on the basis of a comparison of the known gene structures. One group consists of the cytoplasmic (CA I, II, III and VII) and mitochondrial (CA V) members. The other group consists of the membrane-bound (CA IV and IX) and secreted (CA VI) members. In particular, the seven exon/intron boundaries in the CA domain of the CA6 gene are conserved in the CA9 gene, which encodes the multidomain protein CA IX that is overexpressed in tumours and has transforming potential.

Amino Acid Sequence↗
PubMed1999

Mammalian Cdc7-Dbf4 protein kinase complex is essential for initiation of DNA replication.

The Cdc7-Dbf4 kinase is essential for regulating initiation of DNA replication in Saccharomyces cerevisiae. Previously, we identified a human Cdc7 homolog, HsCdc7. In this study, we report the identification of a human Dbf4 homolog, HsDbf4. We show that HsDbf4 binds to HsCdc7 and activates HsCdc7 kinase activity when HsDbf4 and HsCdc7 are coexpressed in insect and mammalian cells. HsDbf4 protein levels are regulated during the cell cycle with a pattern that matches that of HsCdc7 protein kinase activity. They are low in G(1), increase during G(1)-S, and remain high during S and G(2)-M. Purified baculovirus-expressed HsCdc7-HsDbf4 selectively phosphorylates the MCM2 subunit of the minichromosome maintenance (MCM) protein complex isolated by immunoprecipitation with MCM7 antibodies in vitro. Two-dimensional tryptic phosphopeptide-mapping analysis of in vivo (32)P-labeled MCM2 from HeLa cells reveals that several major tryptic phosphopeptides of MCM2 comigrate with those of MCM2 phosphorylated by HsCdc7-HsDbf4 in vitro, suggesting that MCM2 is a physiological HsCdc7-HsDbf4 substrate. Immunoneutralization of HsCdc7-HsDbf4 activity by microinjection of anti-HsCdc7 antibodies into HeLa cells blocks initiation of DNA replication. These results indicate that the HsCdc7-HsDbf4 kinase is directly involved in regulating the initiation of DNA replication by targeting MCM2 protein in mammalian cells.

Amino Acid Sequence↗