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Li JN, Mahmoud MA, Han WF, Ripple M, Pizer ES. Sterol regulatory element-binding protein-1 participates in the regulation of fatty acid synthase expression in colorectal neoplasia. Exp Cell Res 2000; 261:159-65. [PMID: 11082286 DOI: 10.1006/excr.2000.5054] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Endogenous fatty acid synthesis has been observed in certain rapidly proliferating normal and neoplastic tissues. Sterol regulatory element-binding proteins (SREBPs) are transcription factors that regulate the expression of lipogenic genes including fatty acid synthase (FAS), the major biosynthetic enzyme for fatty acid synthesis. We have previously shown that SREBP-1, FAS, and Ki-67, a proliferation marker, colocalized in the crypts of the fetal gastrointestinal tract epithelium. This study sought to determine whether SREBP-1 participates in the regulation of proliferation-associated fatty acid synthesis in colorectal neoplasia. An immunohistochemical analysis of SREBP-1, FAS, and Ki-67 expression in 25 primary human colorectal carcinoma specimens showed colocalization in 22 of these. To elucidate a functional linkage between SREBP-1 activation and proliferation-associated FA synthesis, SREBP-1 and FAS content were assayed during the adaptive response of cultured HCT116 colon carcinoma cells to pharmacological inhibition of FA synthesis. Cerulenin and TOFA each inhibited the endogenous synthesis of fatty acids in a dose-dependent manner and each induced increases in both precursor and mature forms of SREBP-1. Subsequently, both the transcriptional activity of the FAS promoter in a luciferase reporter gene construct and the FAS expression increased. These results demonstrate that tumor cells recognize and respond to a deficiency in endogenous fatty acid synthesis by upregulating both SREBP-1 and FAS expression and support the model that SREBP-1 participates in the transcriptional regulation of lipogenic genes in colorectal neoplasia.
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77
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Kuhajda FP, Pizer ES, Li JN, Mani NS, Frehywot GL, Townsend CA. Synthesis and antitumor activity of an inhibitor of fatty acid synthase. Proc Natl Acad Sci U S A 2000; 97:3450-4. [PMID: 10716717 PMCID: PMC16260 DOI: 10.1073/pnas.97.7.3450] [Citation(s) in RCA: 360] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Compared to normal human tissues, many common human cancers, including carcinoma of the colon, prostate, ovary, breast, and endometrium, express high levels of fatty acid synthase (FAS, EC ), the primary enzyme responsible for the synthesis of fatty acids. This differential expression of FAS between normal tissues and cancer has led to the notion that FAS is a target for anticancer drug development. Recent studies with C75, an inhibitor of fatty acid synthesis, have shown significant antitumor activity with concomitant inhibition of fatty acid synthesis in tumor tissue and normal liver. Importantly, histopathological analysis of normal tissues after C75 treatment showed no adverse effects on proliferating cellular compartments, such as bone marrow, gastrointestinal tract, skin, or lymphoid tissues. In this study, we describe the de novo synthesis of C75 based on the known mechanism of action of cerulenin and the theoretical reaction intermediates of the beta-ketoacyl synthase moiety of FAS. In addition, we demonstrate that C75 is a synthetic, chemically stable inhibitor of FAS. C75 inhibits purified mammalian FAS with characteristics of a slow-binding inhibitor and also inhibits fatty acid synthesis in human cancer cells. Treatment of human breast cancer cells with [5-(3)H]C75 demonstrates that C75 reacts preferentially with FAS in whole cells. Therefore, we have shown that the primary mechanism of the antitumor activity of C75 is likely mediated through its interaction with, and inhibition of, FAS. This development will enable the in vivo study of FAS inhibition in human cancer and other metabolic diseases.
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78
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Li JN, Björk GR. Structural alterations of the tRNA(m1G37)methyltransferase from Salmonella typhimurium affect tRNA substrate specificity. RNA (NEW YORK, N.Y.) 1999; 5:395-408. [PMID: 10094308 PMCID: PMC1369768 DOI: 10.1017/s1355838299980834] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
In Salmonella typhimurium, the tRNA(m1G37)methyltransferase (the product of the trmD gene) catalyzes the formation of m1G37, which is present adjacent and 3' of the anticodon (position 37) in seven tRNA species, two of which are tRNA(Pro)CGG and tRN(Pro)GGG. These two tRNA species also exist as +1 frameshift suppressor sufA6 and sufB2, respectively, both having an extra G in the anticodon loop next to and 3' of m1G37. The wild-type form of the tRNA(m1G37)methyltransferase efficiently methylates these mutant tRNAs. We have characterized one class of mutant forms of the tRNA(m1G37)methyltransferase that does not methylate the sufA6 tRNA and thereby induce extensive frameshifting resulting in a nonviable cell. Accordingly, pseudorevertants of strains containing such a mutated trmD allele in conjunction with the sufA6 allele had reduced frameshifting activity caused by either a 9-nt duplication in the sufA6tRNA or a deletion of its structural gene, or by an increased level of m1G37 in the sufA6tRNA. However, the sufB2 tRNA as well as the wild-type counterparts of these two tRNAs are efficiently methylated by this class of structural altered tRNA(m1G37)methyltransferase. Two other mutations (trmD3, trmD10) were found to reduce the methylation of all potential tRNA substrates and therefore primarily affect the catalytic activity of the enzyme. We conclude that all mutations except two (trmD3 and trmD10) do not primarily affect the catalytic activity, but rather the substrate specificity of the tRNA, because, unlike the wild-type form of the enzyme, they recognize and methylate the wild-type but not an altered form of a tRNA. Moreover, we show that the TrmD peptide is present in catalytic excess in the cell.
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79
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Chen H, Teng L, Li JN, Park R, Mold DE, Gnabre J, Hwu JR, Tseng WN, Huang RC. Antiviral activities of methylated nordihydroguaiaretic acids. 2. Targeting herpes simplex virus replication by the mutation insensitive transcription inhibitor tetra-O-methyl-NDGA. J Med Chem 1998; 41:3001-7. [PMID: 9685239 DOI: 10.1021/jm980182w] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We had previously reported that tetramethyl-O-NGDA (M4N), a synthetic derivative of the naturally occurring nordihydroguaiaretic acid (NDGA), is able to inhibit HIV Tat transactivation by blocking host Sp1 protein at the Sp1 cognate binding site on the HIV LTR promoter. The present studies were undertaken to examine whether M4N is able to inhibit the replication of herpes simplex virus (HSV), another Sp1-regulated virus. The results showed that in Vero cells, M4N inhibits at micromolar levels (IC50 = 43.5 microM) the expression of the herpes immediate early gene (alpha-ICP4), which is essential for HSV replication. An electrophoretic mobility shift assay, examining Sp1 binding to the alpha-ICP4 promoter, showed a significant inhibition of the control bands: 88% inhibition of the fast moving band (FMB) and 45% of the slow moving band (SMB), at 100 microM of drug concentration. Comparative studies between M4N and acycloguanosine (acyclovir, ACV) in cultured Vero cells revealed an interesting pattern in the drug sensitivity (IC50) and cytotoxicity (TC50) parameters. For M4N, the IC50 varied between 11.7 and 4 microM in 10 passages of HSV-1 and 4 passages of HSV-2 with no indication for a requirement of higher drug concentration. In contrast, for acyclovir, the IC50 increased from 7 microM in the first passage to 444 microM in the tenth passage of HSV-1, and >88 microM for the fourth passage of HSV-2, indicating a rapid build-up of drug resistance against acyclovir. While the selective index (SI), defined as the ratio: TC50/IC50, remained relatively constant for M4N; it dropped 60-fold for acyclovir in the endpoints of viral passages. Drug sensitivity for M4N toward the acyclovir-sensitive strain (sm44) and the acyclovir-resistant strain (ACV-10) of HSV-1 was similar, indicating no cross-resistance between M4N and acyclovir in their anti-HSV effects. These results may have an important clinical relevance since HSV has been shown to be a factor for spreading of HIV.
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80
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Qian Q, Li JN, Zhao H, Hagervall TG, Farabaugh PJ, Björk GR. A new model for phenotypic suppression of frameshift mutations by mutant tRNAs. Mol Cell 1998; 1:471-82. [PMID: 9660932 DOI: 10.1016/s1097-2765(00)80048-9] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
According to the prevailing model, frameshift-suppressing tRNAs with an extra nucleotide in the anticodon loop suppress +1 frameshift mutations by recognizing a four-base codon and promoting quadruplet translocation. We present three sets of experiments that suggest a general alternative to this model. First, base modification should actually block such a four-base interaction by two classical frameshift suppressors. Second, for one Salmonella suppressor tRNA, it is not mutant tRNA but a structurally normal near cognate that causes the +1 shift in-frame. Finally, frameshifting occurs in competition with normal decoding of the next in-frame codon, consistent with an event that occurs in the ribosomal P site after the translocation step. These results suggest an alternative model involving peptidyl-tRNA slippage at the classical CCC-N and GGG-N frameshift suppression sites.
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81
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Li JN, Björk GR. 1-Methylguanosine deficiency of tRNA influences cognate codon interaction and metabolism in Salmonella typhimurium. J Bacteriol 1995; 177:6593-600. [PMID: 7592438 PMCID: PMC177513 DOI: 10.1128/jb.177.22.6593-6600.1995] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
1-Methylguanosine (m1G) is present next to the 3' end of the anticodon (position 37) in tRNA(1,2,3,Leu), tRNA(1,2,3,Pro), and tRNA(3Arg). A mutant of Salmonella typhimurium lacks m1G in these seven tRNAs when grown at or above 37 degrees C, as a result of a mutation (trmD3) in the structural gene (trmD) for the tRNA(m1G37)methyltransferase. The m1G deficiency induced 24 and 26% reductions in the growth rate and polypeptide chain elongation rate, respectively, in morpholinepropanesulfonic acid (MOPS)-glucose minimal medium at 37 degrees C. The expression of the leuABCD operon is controlled by the rate with which tRNA(2Leu) and tRNA(3Leu) read four leucine codons in the leu-leader mRNA. Lack of m1G in these tRNAs did not influence the expression of this operon, suggesting that m1G did not influence the efficiency of tRNA(2,3Leu). Since the average step time of the m1G-deficient tRNAs was increased 3.3-fold, the results suggest that the impact of m1G in decoding cognate codons may be tRNA dependent. The trmD3 mutation rendered the cell more resistant or sensitive to several amino acid analogs. 3-Nitro-L-tyrosine (NT), to which the trmD3 mutant is sensitive, was shown to be transported by the tryptophan-specific permease, and mutations in this gene (mtr) render the cell resistant to NT. Since the trmD3 mutation did not affect the activity of the permease, some internal metabolic step(s), but not the uptake of the analog per se, is affected. We suggest that the trmD3-mediated NT sensitivity is by an abnormal translation of some mRNA(s) whose product(s) is involved in the metabolic reactions affected by the analog. Our results also suggest that tRNA modification may be a regulatory device for gene expression.
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82
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Ma YG, Wang DM, Li JN, Zhu HY. Cardiac function and histological changes after non-dynamic cardiomyoplasty and preliminary study of dynamic cardiomyoplasty. Chin Med J (Engl) 1994; 107:836-9. [PMID: 7867391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
By means of histological method and ultrasound cardiographic (UCG) examination, the left-right ratio of transectional area of muscle fiber of latissimus dorsi muscle (LDM) after non-dynamic cardiomyoplasty was 77.4 +/- 11.7% in Group I (3 weeks after operation), and 78.4 +/- 11.6% atrophy and hyperplasia of LDM, but the basical structure was retained. The ejection fraction (EF) decreased significantly after operation (P < 0.05), but the difference between two groups was non- significant. Also, dynamic cardiomyoplasty was performed on a sheep. UCG showed the increased cardiac systolic function after operation. ATPase, succinodehydrogenase (SDH) and PAS examination implied the strengthening of fatigue-resistant ability in skeletal muscles after long-term electrical stimulation. So cardiomyoplasty is suggested to be a supplementary measure in treating end-stage heart failure.
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83
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Sun SX, Li JN, Pan KF, Zhang JK, Zhou XJ, Liu K, Li Z, Cai RF. [On the educational aspects of esthetic stomatology]. SHANGHAI KOU QIANG YI XUE = SHANGHAI JOURNAL OF STOMATOLOGY 1993; 2:166-8. [PMID: 15159834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
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84
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Gerber A, Li JN, Tarnawski Z, Franse JJ, Menovsky AA. Magnetic instabilities in high-temperature superconductors under rapidly varying magnetic fields. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 47:6047-6053. [PMID: 10004553 DOI: 10.1103/physrevb.47.6047] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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85
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Wilcox I, Ben Freedman SB, Li JN, Harris PJ, Kelly DT. Comparison of exercise stress testing with ambulatory electrocardiographic monitoring in the detection of myocardial ischemia after unstable angina pectoris. Am J Cardiol 1991; 67:89-91. [PMID: 1986510 DOI: 10.1016/0002-9149(91)90106-u] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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86
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Li JN. [Applied anatomy of dorsal nasal fascia for augmentative rhinoplasty]. ZHONGHUA ZHENG XING SHAO SHANG WAI KE ZA ZHI = ZHONGHUA ZHENG XING SHAO SHANG WAIKF [I.E. WAIKE] ZAZHI = CHINESE JOURNAL OF PLASTIC SURGERY AND BURNS 1990; 6:247. [PMID: 2282576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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87
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Hagervall TG, Ericson JU, Esberg KB, Li JN, Björk GR. Role of tRNA modification in translational fidelity. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1050:263-6. [PMID: 2207153 DOI: 10.1016/0167-4781(90)90178-5] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In transfer RNA many different modified nucleosides are found, especially in the anticodon region. In this region, pseudouridine (psi) is found in positions 38, 39 or 40 in a subset of tRNA species, 2-methylthio-6-hydroxyisopentenyladenosine (ms2io6A) is found in position 37 in tRNAs that read codons starting with U and 1-methylguanosine (m1G) is found in position 37 in tRNAs reading codons of the UCCNG type. We have used the mutants hisT, miaA and miaB and trmD, which are deficient in the biosynthesis of psi, ms2io6A, and m1G, respectively, to study the functional aspects of the respective modified nucleosides. We have shown: (1) Presence of psi improved the cellular growth rate, the polypeptide step-time, and the efficiency of an amber suppressor, but did not appreciably sense the codon context. (2) Presence of ms2io6A improved the cellular growth rate, the polypeptide step-time and the efficiency of several amber suppressor tRNAs. It also had a profound effect on the codon context sensitivity of the tRNA. (3) Presence of m1G improved the cellular growth rate and the polypeptide steptime and also prevented the tRNA from shifting the reading frame. Thus, these three modified nucleosides present in the anticodon region have apparently different functions.
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88
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Li JN, Li Y, Chan JB. [A study of 217 cases of IGA nephropathy]. ZHONGHUA NEI KE ZA ZHI 1987; 26:266-8, 317-8. [PMID: 3652831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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89
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Li JN. [Immediate reconstruction of soft tissue defects in legs and feet]. ZHONGHUA ZHENG XING SHAO SHANG WAI KE ZA ZHI = ZHONGHUA ZHENG XING SHAO SHANG WAIKF [I.E. WAIKE] ZAZHI = CHINESE JOURNAL OF PLASTIC SURGERY AND BURNS 1985; 1:53-4. [PMID: 3939770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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90
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Kong FG, Li JN. [Ectropion of the eyelid due to maxillary osteitis and its treatment (report on 26 cases)]. ZHONGHUA ZHENG XING SHAO SHANG WAI KE ZA ZHI = ZHONGHUA ZHENG XING SHAO SHANG WAIKF [I.E. WAIKE] ZAZHI = CHINESE JOURNAL OF PLASTIC SURGERY AND BURNS 1985; 1:28-30. [PMID: 3939786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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91
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Li N, Yang ZC, Jiang KY, Chen FM, Wang TY, Lian WK, Wu CZ, You ZJ, Li JN, Wei JJ. Effect of intravenous infusion on development of pulmonary oedema after inhalation injury. Burns 1983; 9:394-400. [PMID: 6616307 DOI: 10.1016/0305-4179(83)90102-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Last year, after a systematic search of pathological and patho-physiological changes of inhalation injury in dogs, we recorded severe pulmonary oedema as early as 2 h postburn (the earliest monitoring time designed in experiment) on dogs inflicted with both body surface and severe respiratory burns without any fluid replacement during the whole course of experiment. In an analysis of cases admitted into our burn centre in the past ten years, we also found that there was no definite relationship between the incidence and severity of pulmonary oedema occurring in severe burn patients and the amount of fluid infused in the early burn phase. These facts led us to the following experiment designed to study the effect of intravenous infusion on development of pulmonary oedema after severe burns complicated with inhalation injuries.
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