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Biomedical subjects

D W Kim

Publications and source records attributed to D W Kim.

At least 91 records · Page 5Linked to original sources
PubMed2001

Changes in autoimmune thyroid disease following allogeneic bone marrow transplantation.

Autoimmune diseases can be transmitted and eliminated by bone marrow transplantation (BMT). There have been several cases of autoimmune thyroid disease (AITD) occurring after BMT, but AITD remission has been rarely reported. We present four cases in which the remission or transfer of AITD occurred after an allogeneic BMT. Two patients with severe aplastic anemia (SAA) showed evidence of remission of Hashimoto's thyroiditis which they had before allogeneic BMT. One patient with SAA, which developed during treatment with propylthiouracil for Graves' disease, underwent allogeneic BMT and showed evidence of Graves' disease remission following BMT. In one patient, new AITD occurred after an allogeneic BMT from an HLA-matched sibling who already had AITD. These cases support the evidence that the immune system is newly reconstituted after BMT, and severe autoimmune disease can be an indication for BMT. To fully understand the real changes in autoimmune status after BMT, long-term prospective studies are necessary.

Adolescent↗
PubMed2001

The kinetics of circulating cytokines including IL-6, TNF-alpha, IL-8 and IL-10 following allogeneic hematopoietic stem cell transplantation.

Pro-inflammatory (IL-6, TNFalpha and IL-8) and anti-inflammatory (IL-10) cytokines were determined in weekly samples from 52 patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT). IL-6 increased immediately after transplant peaking at week +3, but IL-8 concentrations were elevated only during week +1. After a slight decrease in week +1, TNF-alpha significantly increased from week +2 and peaked at week +3, whereas, IL-10 values started to rise in week +2 and peaked during week +4. IL-6 and TNF-alpha were positively correlated from week +2 to week +4, and IL-6 levels at week +1 were related with fever and severe stomatitis. Serum levels of IL-6 at week +1 and IL-10 at week +4 were significantly higher in patients with early transplant-related complications, such as fever, severe stomatitis or acute GVHD > or = overall grade II than in those without the complications. We conclude that a high serum IL-6 level at week +1 may be an early predictor of transplant-related complications and that it seems to trigger pro- and anti-inflammatory cytokine release. Kinetic patterns of IL-6 and IL-10 were more exaggerated in those with complications after HSCT.

Acute Disease↗
PubMed2001

Evaluation of survival rate after follicular unit transplantation using the KNU implanter.

BACKGROUND: Many hair transplant surgeons have advocated the use of micrograft megasessions for the purpose of a more natural looking end result, especially in the Oriental with higher skin/hair color contrast and darker, coarse, straight hairs. But it also has some fundamental limitations. Most important are a low graft yield and a low density after transplantation. There are several reports about the survival rate of micrografts in Caucasians, though the results are variable, but few reports about the survival rate and fate of micrografts in Orientals. OBJECTIVE: To compare the survival rate of one-hair follicular units with that of two-hair follicular units using the KNU implanter, to ascertain the average survival rate of micrografts (one- and two-hair follicular units), and to evaluate the fate of grafted hair according to time. METHODS: Two templates of 1.5 cm2 were made by tattooing on both sides of the frontoparietal recess areas in 11 patients with male pattern baldness (beyond Norwood type IIIa). The authors planted one-hair unit micrografts in the left template and two-hair unit micrografts in the right template, which were prepared by the concept of follicular unit, and counted the surviving number of follicular units at 1 and 3 months and total hairs at 6 and 12 months after transplantation. RESULTS: The mean survival rate by the number of follicular units was 47.3 and 57.4% at 1 and 3 months after transplantation, respectively. The mean survival rate by the total number of hairs was 92.0 and 90.4% at 6 and 12 months after transplantation, respectively. CONCLUSION: About 50% of the transplanted hairs fell out in 1 month, but at 6 months the survival rate of follicular unit transplantation using the KNU implanter showed a good result (92%), and there were no significant differences in the mean survival rate of follicular unit and total hairs between one-hair and two-hair units at 1, 3, 6, and 12 months after transplantation.

Adult↗
PubMed2001

Arthroscopic anterior cruciate ligament reconstruction with quadriceps tendon composite autograft.

At present, no single graft option clearly outperforms another. Autografts (patellar tendon, hamstring) and allografts (Achilles tendon, patellar tendon) are the grafts most often used. However, each grafts has advantages and disadvantages. Quadriceps tendon graft for anterior cruciate ligament reconstruction is not new, but an alternative composite graft is introduced here that consists of quadriceps tendon-patellar bone and bone obtained from a coring reamer used to create the tibial tunnel. This composite graft retains reduced morbidity while allowing the secure bone-to-bone fixation associated with bone-patellar tendon-bone graft.

Anterior Cruciate Ligament↗
PubMed2001

Liposome-encapsulated tumor necrosis factor-alpha enhances the effects of radiation against human colon tumor xenografts.

Recent reports have shown that tumor necrosis factor-alpha (TNF-alpha) can augment the effects of radiation against certain tumor types. However, the high concentrations of intravenous infusion of TNF-alpha needed to cause tumor regression can induce many systemic side effects. The aims of this study were to determine if TNF-alpha encapsulated in sterically stabilized (Stealth, ALZA Corporation, Mountain View, CA), PEGylated liposomes (SL) augments the antitumor effects of radiation and to compare its efficacy and possible toxicity with free TNF-alpha in the LS174T human colon tumor xenograft model. Nude mice were injected subcutaneously (s.c.) with LS174T cells and treated intravenously (i.v.) with Stealth-liposomal TNF-alpha (SL-TNF-alpha) with and without radiation or TNF-alpha with or without radiation when tumor size was approximately 200 mm(3). In phase 1, a significant decrease (p = 0.047) in tumor growth was observed with radiation at day 21 but not with SL-TNF-alpha or free TNF-alpha alone. By the end of phase 1 (day 27) with continued treatments, the SL-TNF-alpha plus radiation group had significantly smaller tumors (p = 0.044) than those in the free TNF-alpha plus radiation group. In phase 2, where a similar tumor growth reduction pattern was observed, the addition of TNF-alpha to radiation, either as free protein or within SL, increased lymphocyte activation and natural killer (NK) cell numbers in both blood and spleen. The effect was generally more pronounced with SL-TNF-alpha. Systemic toxicity, based on hematologic analyses and body weight, was absent or minimal. Collectively, the data show that pretreatment with SL-TNF-alpha can enhance more effectively, and possibly more safely, the effects of radiation against human colon tumor xenografts than can free TNF-alpha and that the increased antitumor action may involve upregulation of lymphocytes.

Animals↗
PubMed2001

The effect of noise on the bispectral index during propofol sedation.

UNLABELLED: Because noise in the operating room has been alleged to interfere with the ability to sedate patients before surgery, we evaluated the effect of noise on the Bispectral index (BIS) value during propofol sedation. Thirty unpremedicated patients were studied before the start of surgery while receiving propofol sedation on two separate occasions according to a randomized, crossover protocol design. After achieving a stable baseline BIS value of either 75 or 80 with a target-controlled infusion of propofol, an external sound source administered noise at 50, 80, 110, and 120 dB. The changes in the BIS value were recorded over a 1-min interval at each noise level. In the BIS 75 group, increasing levels of noise did not significantly alter the BIS value. However, in the BIS 80 group, the BIS values at 80, 110, and 120 dB were significantly higher compared to the value at 50 dB. In conclusion, experimental noise increases the BIS and appears to have a greater effect on the BIS value at "lighter" levels of propofol sedation. IMPLICATIONS: Experimental noise levels can increase the Bispectral index (BIS) values during propofol sedation in the operating room. However, the magnitude of the BIS response is influenced by the depth of sedation.

Adult↗
PubMed2001

A noninvasive estimation of hypernasality using a linear predictive model.

The pronunciation of a speaker with a defective soft palate is marked by hypernasality and an operation may be necessary to repair the defective soft palate to reduce this hypernasality. An assessment of hypernasality is necessary to quantify the effect of the surgery. The current clinical methods for assessing hypernasality are uncomfortable or require expensive equipment. In this paper, a new quantitative method is proposed to estimate hypernasality. This method requires only a microphone and a personal computer equipped with a sound card. Zeros in the frequency response of the vocal tract system are one of the major characteristics of hypernasality. The proposed method made use of the fact that a linear predictive model with a typical order for the human vocal tract system is not accurate when the vocal tract system has zeros in its frequency response. Hypernasality was estimated by comparing the distance between the sequences of linear predictive cepstrum of low- and high-order linear predictive models. The proposed method provides a better correlation (0.58) with nasalance measured by a nasometer than Teager method (0.44) for all the data. Furthermore, the proposed method showed higher correlation of 0.84 than 0.71 of the Teager method for data with a nasalance higher than 35%. Since the proposed method needs only digitized speech data, it is much less invasive and provides an easy and cost-effective evaluation of hypernasality.

Biomedical Engineering↗
PubMed2001

Resveratrol inhibits phorbol ester and UV-induced activator protein 1 activation by interfering with mitogen-activated protein kinase pathways.

Resveratrol, a phenolic compound found in grapes and other food products, prevents chemical-induced carcinogenesis in a number of animal models of cancers. To better understand its chemopreventive property, we examined effects of resveratrol on the activity of activator protein 1 (AP-1), a dimeric transcription factor that plays a critical role in the carcinogenesis and tumor transformation. Pretreatment of HeLa cells with resveratrol inhibited the transcription of AP-1 reporter gene by UVC and phorbol 12-myristate 13-acetate (PMA). Pretreatment with resveratrol also inhibited the activation of extracellular signal-regulated protein kinase 2 (ERK2), c-jun N-terminal kinase 1 (JNK1), and p38. Selectively blocking mitogen-activated protein kinase (MAPK) pathways by overexpression of dominant-negative mutants of kinases attenuated the AP-1 activation by PMA and UVC. Interestingly, resveratrol had little effect on the induction of AP-1 reporter gene by active Raf-1, MEKK1, or MKK6, suggesting that it inhibited MAPK pathways by targeting the signaling molecules upstream of Raf-1 or MEKK1. Indeed, incubation of resveratrol with the isolated c-Src protein tyrosine kinase and protein kinase C diminished their kinase activities. Furthermore, inhibition of protein tyrosine kinases and protein kinase C with their selective inhibitors impaired the activation of MAPKs as well as the induction of AP-1 activity by PMA and UVC. In addition, modulation of estrogen receptor activity with 17beta-estradiol had no effect on the inhibition of AP-1 by resveratrol. Taken together, these results suggest that the effects of resveratrol on AP-1 and MAPK pathways may involve the inhibition of both protein tyrosine kinases and protein kinase C.

Anticarcinogenic Agents↗
PubMed2001

JAK2 activates TFII-I and regulates its interaction with extracellular signal-regulated kinase.

TFII-I is a transcription factor that shuttles between the cytoplasm and nucleus and is regulated by serine and tyrosine phosphorylation. Tyrosine phosphorylation of TFII-I can be regulated in a signal-dependent manner in various cell types. In B lymphocytes, Bruton's tyrosine kinase has been identified as a TFII-I tyrosine kinase. Here we report that JAK2 can phosphorylate and regulate TFII-I in nonlymphoid cells. The activity of TFII-I on the c-fos promoter in response to serum can be abolished by dominant negative JAK2 or the specific JAK2 kinase inhibitor AG490. Consistent with this, we have also found that JAK2 is activated by serum stimulation of fibroblasts. Tyrosine 248 of TFII-I is phosphorylated in vivo upon serum stimulation or JAK2 overexpression, and mutation of tyrosine 248 to phenylalanine inhibits the ability of JAK2 to phosphorylate TFII-I in vitro. Tyrosine 248 of TFII-I is required for its interaction with and phosphorylation by ERK and its in vivo activity on the c-fos promoter. These results indicate that the interaction between TFII-I and ERK, which is essential for its activity, can be regulated by JAK2 through phosphorylation of TFII-I at tyrosine 248. Thus, like the STAT factors, TFII-I is a direct substrate of JAK2 and a signal-dependent transcription factor that integrates signals from both tyrosine kinase and mitogen-activated protein kinase pathways to regulate transcription.

3T3 Cells↗
PubMed2001

FcgammaRIIa/IIIa polymorphism and its association with clinical manifestations in Korean lupus patients.

The aim of this study was to determine the distribution of the FcgammaRlla and FcgammaRIIIa polymorphisms and their association with clinical manifestations in Korean lupus patients. Three hundred SLE (systemic lupus erythematosus) patients (48 male, 252 female) meeting 1982 ACR criteria and 197 Korean disease-free controls were enrolled. Genotyping for FcgammaRlla 131 R/H and FcgammaRIIIa 176 F/V was performed by PCR of genomic DNA using allele-specific primers and the FcgammaRIIIa genotype was confirmed by direct sequencing of PCR product in some cases. There was significant skewing in the distribution of the three FcgammaRIIa genotypes between the SLE and the controls (P=0.002 for R/R131 vs R/H131 and H/H131, OR 2.5 (95% Cl 1.4-4.5), but not in FcgammaRIIIa genotypes. FcgammaRIIa-R allele was a significant predictor of lupus nephritis, as compared with SLE patients without nephritis (P=0.034 for R131 vs H131, OR 1.4 (95% Cl 1.03-1.9)), but proliferative nephritis (WHO class III and IV) was less common in patients with FcgammaRlla-R/R131 and in FcgammaRIIa-R allele. In 300 SLE patients, high binding allele combination H131/V176 was less common in SLE with nephritis than in SLE without nephritis. Hemolytic anemia was less common in R131/F176 allele combination among four FcgammaRIIa/FcgammaRIIIa allelic combinations. Male SLE patients showed a higher frequency of renal involvement, serositis, thrombocytopenia, malar rash and discoid rash than female SLE, and male SLE had a higher frequency of FcgammaRIIa-R/R131 or R131-allele than male controls, but FcgammaRIIa or FcgammaRIIIa genotypes had no association with renal involvement in male SLE patients. FcgammaRIIa-H/H131 showed a higher frequency of hemolytic anemia and less pulmonary complications in male SLE. Female SLE patients showed higher frequency of any hematologic abnormality, lymphopenia, anticardiolipin antibody (+) and anti-Ro antibody (+) than male SLE, and had earlier onset of first symptoms. There was no skewing in FcgammaRIIa or FcgammaRIIIa genotypes between female SLE and female controls, but FcgammaRIIa-R131 allele showed skewing between female SLE with nephritis and female SLE without nephritis. The age at onset of thrombocytopenia was earlier in FcgammaRIIa R/R131 among three FcgammaRIIa genotypes, and serositis in FcgammaRIIIa-F/F176 among three FcgammaRIIIa genotypes. FcgammaRIIa-R131 homozygote was a major predisposing factor to the development of SLE and FcgammaRIIa-RI31 homozygote and R131 allele were a predisposing factor, and H131/V176 was a protective allele combination in lupus nephritis. In contrast to other ethnic patients, in our study cohort, clinical manifestation was different between male and female, and FcgammaRIIa and FcgammaRIIIa showed somewhat different clinical associations between the genders.

Adolescent↗
PubMed2001

Incorporation of sulfonylurea into N-isopropylacrylamide as an extracellular matrix for an artificial pancreas.

High-molecular-weight N-isopropylacrylamide copolymers with small amounts of sulfonylurea (SU, typically 2-4 mol% in the feed) were synthesized by free radical polymerization in benzene. SU-incorporated polymer solutions (5, 6, 8, and 10% w/v) in a culture medium (pH 7.4, 0.15 M ionic strength) with islet cells were mixed and poured into Millicells which supported gel formation. In order to increase the gelation temperature, the SU-incorporated copolymer gel, p(NiPAAm-co-SU), was blended with the p(NiPAAm-co-AAc) polymer at a ratio of 4 to 96. Interaction between the islet cells and the synthetic matrix of SU-incorporated copolymer gel resulted in effective cell viability and such cell functions as insulin secretion. To verify the specific interaction between the SU (K+ channel closer)-incorporated copolymer and islet cells, the cells were pretreated with diazoxide, an agonist of the ATP-sensitive K+ channel (K+ channel opener), before interaction between the polymer and islet cells. This treatment suppressed the action of SU on the islet cells. The results from this study provide evidence that the SU-incorporated copolymer stimulated insulin secretion by specific interaction between SU moieties in the polymer and the islet cells.

Acrylamides↗
PubMed2001

Magnetic resonance imaging of the bone marrow after bone marrow transplantation or immunosuppressive therapy in aplastic anemia.

To compare magnetic resonance (MR) images of the bone marrow (BM) after bone marrow transplantation or immunosuppressive therapy in patients with aplastic anemia (AA), MR imaging of BM was reviewed retrospectively in 16 patients (13 males and 3 females, mean age 26 yr) with AA who completely responded clinically after transplantation or immunosuppressive therapy. The signal intensity (SI) of BM was classified into four patterns according to the increasing amount of cellular marrow, i.e., pattern I to IV. SI of MR imaging of BM exhibited an increase of cellular marrows following both transplantation and immunosuppressive therapy. Of the eight patients on transplantation, the SI of the lumbar spinal BM was pattern III in two patients and IV in six on T1-weighted and short tau inversion recovery (STIR) images. In the eight patients with immunosuppressive therapy, the SI of the lumbar spinal BM was pattern II in one, III in five, and IV in two on T1-weighted images and pattern II in one, III in four, and IV in three on STIR images. SI on MR imaging of the lumbar spinal BM showed a more cellular pattern in patients on transplantation than in those on immunosuppressive therapy.

Adolescent↗
PubMed2001

Analysis of polymorphic regions of Plasmodium vivax Duffy binding protein of Korean isolates.

The present study was designed to investigate polymorphism in Duffy binding protein (DBP) gene of Plasmodium vivax isolates of Korea. Thirty samples were obtained from P. vivax patients in Yonchon-gun, Kyonggi-do in 1998. The PCR products of the samples were subjected to sequencing and hybridization analyses of the regions II and IV of P. vivax DBP gene. Two genotypes, SK-1 and SK-2, were identified on the basis of amino acid substitution and deletion. The genotype of 10 isolates was SK-1 and that of 20 isolates was SK-2. Most of the predicted amino acids in the region II of DBP gene were conserved between the Korean isolates and Belem strain except for 4-5 amino acid substitutions. In the region IV of DBP, a 6-bp insert that was shown in the Sal-1 allele type was found in SK-1, and a 27-bp insert that was shown in the Papua New Guinea allele type was found in SK-2. In conclusion, the present findings suggest that two genotypes of P. vivax coexist in the endemic area of Korea.

Amino Acid Sequence↗
PubMed2001

Hematopoietic stem cell transplantation for high-risk adult patients with severe aplastic anemia; reduction of graft failure by enhancing stem cell dose.

BACKGROUND AND OBJECTIVES: The main causes of failure after allogeneic hematopoietic stem cell transplantation (HSCT) in patients with severe aplastic anemia (SAA) are graft-versus-host disease (GVHD), infection and graft failure, often exacerbated by large numbers of transfusions and prolonged disease duration before transplant. This study retrospectively analyzes the outcome and factors related to survival or graft failure in high-risk patients with SAA receiving HSCT in our institution. DESIGN AND METHODS: Between January 1995 and December 1999, 40 consecutive adult patients who were multi-transfused (more than 40 units of red blood cells +/- platelets) and/or had a 3 years or longer period prior to transplant were enrolled. Their median age was 27.5 years (range, 16 to 43) and 21 (52.5%) were women. All donors were human leukocyte antigen (HLA)-matched siblings. Before transplant, 29 patients (72.5%) received a course of antithymocyte globulin (ATG) and cyclosporin A (CsA). The median interval from diagnosis to transplant was 59 months (range, 2 to 216). The median number of transfusions was 115 units (range, 10 to 480). All patients received a conditioning regimen of cyclophosphamide, ATG, and procarbazine. Our patients received either bone marrow (BM) alone (n=20) or BM+peripheral blood stem cells (PBSC) (n=20) as a stem cell source. T-cells of PBSC were depleted using the CD34 enrichment method. GVHD prophylaxis consisted of CsA and short-term methotrexate. RESULTS: In the BM+PBSC group, neutrophil recovery to 0.5 x 10(9)/L and platelet recovery to 20 x 10(9)/L were achieved more rapidly than in the BM group (p=0.005 and 0.039, respectively). The incidences of graft failure, grade II to IV acute GVHD, and chronic GVHD were 22.5%, 12.8% and 23.1%, respectively. Graft failure occurred in 2 of 20 patients (10%) receiving BM+PBSC and in 7 of 20 (35%) receiving BM alone (p=0.069). Seven of 9 patients who had graft failure received a booster treatment and recovered normal marrow function. GVHD incidence was comparable between the BM+PBSC and BM groups. Six patients (15%) died from graft failure (n=2), interstitial pneumonia (n=2), cyclophosphamide-induced heart failure (n=1), and chronic GVHD followed by pneumonia (n=1). The Kaplan-Meier estimate of survival was 83.7% with a median follow-up duration of 40.5 months (range 8-67). In multivariate analysis only chronic GVHD adversely influenced survival (p=0.042). INTERPRETATION AND CONCLUSIONS: These results suggest that HSCT is an effective treatment for multi-transfused SAA patients with prolonged disease duration. It is highly possible that the infusion of a large number of stem cells leads to a reduction of graft failure and a faster speed of engraftment. Booster treatment is successful in achieving engraftment in patients with graft failure.

Adolescent↗
PubMed2000

The RelA NF-kappaB subunit and the aryl hydrocarbon receptor (AhR) cooperate to transactivate the c-myc promoter in mammary cells.

NF-kappaB/Rel transcription factors regulate many genes involved in control of cellular proliferation, neoplastic transformation, and apoptosis, including the c-myc oncogene. Recently, we have observed that levels of NF-kappaB and aryl hydrocarbon receptor (AhR), which mediates malignant transformation by environmental carcinogens, are highly elevated and appear constitutively active in breast cancer cells. Rel factors have been found to functionally interact with other transcription factors. Here we demonstrate a physical and functional association between the RelA subunit of NF-kappaB and AhR resulting in the activation of c-myc gene transcription in breast cancer cells. RelA and AhR proteins were co-immunoprecipitated from cytoplasmic and nuclear extracts of non-malignant MCF-10F breast epithelial and malignant Hs578T breast cancer cells. In transient co-transfection, RelA and AhR gene products demonstrated cooperation in transactivation of the c-myc promoter, which was dependent on the NF-kappaB elements, and in induction of endogenous c-Myc protein levels. A novel AhR/RelA-containing NF-kappaB element binding complex was identified by electrophoretic mobility shift analysis of nuclear extracts from RelA and AhR co-transfected Hs578T cells. Thus, the RelA and AhR proteins functionally cooperate to bind to NF-kappaB elements and induce c-myc gene expression. These findings suggest a novel signaling mechanism whereby the Ah receptor can stimulate proliferation and tumorigenesis of mammary cells.

Binding Sites↗
PubMed2000

Requirement for the COOH-terminal pro-sequence in the translocation of aqualysin I across the cytoplasmic membrane in Escherichia coli.

Aqualysin I from Thermus aquaticus YT-1 is an extracellular subtilisin-type serine protease. The protease is synthesized as a distinct precursor composed of four functional domains: an N-terminal signal sequence, an N-terminal pro-sequence, a protease domain, and a C-terminal pro-sequence. The N-terminal pro-sequence is essential for the production of active aqualysin I while the C-terminal pro-sequence is required for extracellular secretion of aqualysin I. In an E. coli expression system, the function of C-terminal pro-sequence in the translocation of aqualysin I across the cytoplasmic membrane was investigated. More than 60-70% of the total activity was detected in the cytoplasmic fraction in the deletion mutations of the C-terminal pro-sequence while less than 30% was found in this fraction in wild type. In addition, in vitro processing of aqualysin I precursors with these mutations to a mature form promptly occurred and the folding into active aqualysin I was rapid. These results suggest that the C-terminal pro-sequence, probably in conjunction with the signal sequence, facilitates the translocation of the precursor across the cytoplasmic membrane by preventing the precursor from taking on an active conformation.

Cell Membrane↗
PubMed2000

The endonuclease activity of the yeast Dna2 enzyme is essential in vivo.

Dna2 is a multifunctional enzyme in yeast that possesses endonuclease activity well suited to remove RNA-DNA primers of Okazaki fragments, raising the question of whether endonuclease activity is essential for in vivo Dna2 function. Systematic site-directed mutations of amino acid residues in Saccharomyces cerevisiae DNA2 conserved in the central region of many eukaryotic DNA2 homologs allowed us to identify mutant dna2 alleles that were divided into three groups based on the viability of the mutant cells: (i) viable; (ii) inviable only when expression was repressed; (iii) inviable. Biochemical analyses of recombinant mutant Dna2 proteins isolated from the latter two groups revealed that they possessed normal ATPase/helicase activity, but were impaired in their endonuclease activity. Cells expressing mutant Dna2 enzymes partially impaired in endonuclease activity were viable, but were unable to grow when expression of their mutant Dna2 enzymes was further reduced. Their growth was restored when the mutant Dna2 proteins decreased in nuclease activity were induced to overexpress. In contrast, mutant Dna2 proteins lacking endonuclease activity did not allow cells to grow under any conditions tested. These in vivo and in vitro results demonstrate that the endonuclease activity of Dna2 is essential for Okazaki fragment processing.

Adenosine Triphosphatases↗