Atypical Transfer RNA's And Their Origin In Neoplastic Cells

Borek, Ernest; Kerr, Sylvia J.

doi:10.1016/s0065-230x(08)60374-7

Cited by 171 publications

(31 citation statements)

References 73 publications

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“…These modified nucleosides are primary constituents of transfer ribonucleic acid (tRNA) and are synthesized at the macromolecular level [5]. When tRNA is catabolized, most of these modified nucleosides cannot be reutilized; consequently, they are excreted.…”

Section: Introductionmentioning

confidence: 99%

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Clinical significance and prognostic value of urinary nucleosides in breast cancer patients

Zheng

Kong

Xiong

et al. 2005

Clinical Biochemistry

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Section: Introductionmentioning

confidence: 99%

“…The molecular mechanisms of this excretion are unclear. It is known that extracts of neoplastic tissues have aberrant tRNA methyltransferases [5], and it has been suggested that the high turnover of tRNA is due to rapid degradation of aberrantly modified tRNAs [5,6].…”

Section: Introductionmentioning

confidence: 99%

Clinical significance and prognostic value of urinary nucleosides in breast cancer patients

Zheng

Kong

Xiong

et al. 2005

Clinical Biochemistry

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“…However, in order to postulate an effect on altered patterns of methylation such has been reported for a number of biological systems (8), it is necessary to show that an inhibitor or stimulator produces differential effects on the various specific tRNA methylating enzymes. Work in this area has been hampered by the unavailability of individual purified tRNA methytransferases.…”

Section: Introductionmentioning

confidence: 99%

S-Adenosylhomocysteine inhibition of three purified tRNA methyltransferases from rat liver

1975

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Three tRNA methyltransferases from rat liver have been fractionated and purified greater than 100-fold. These enzymes have been examined for their sensitivity to inhibition by S-adenosylhomocysteine (SAH). The methyltransferase which forms m2-guanine in the region between the dihydrouridine loop and the acceptor stem of tRNA (m2-guanine methyltransferase I) is least sensitive to SAH inhibition, with a Ki of 8 PM. The enzyme responsible for forming m2guanine between the dihydrouridine and anticodon loops (m2-guanine methyltransferase II) has a Ki of 0.3 PM, while ml-adenine methyltransferase shows intermediate sensitivity to SAH (Ki = 2.4 "PM). All three methyltransferases have similar Km's for the S-adenosylmethionine substrate (1.5-2.0 PM). These results are consistent with the hypothesis that activity of individual tRNA methyltransferases may be controlled by enzyme systems which alter cellular SAH levels.

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“…1-3). Various techniques have been used in attempts to detect unique tRNA species in tumor cells, and it has been found that the amount of methylated nucleosides in tRNA and the activities of tRNA methylases are generally high in tumor tissues (3,4). However, analyses of modified nucleosides using total unfractionated tRNA have given results dependent upon the tumor tissues examined (5).…”

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confidence: 99%

Detection of unique tRNA species in tumor tissues by Escherichia coli guanine insertion enzyme.

Okada¹,

Shindo-Okada²,

Sato³

et al. 1978

Proc. Natl. Acad. Sci. U.S.A.

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The guanine insertion enzyme from Escherichia coli catalyzes exchange of guanine located at the first position of the anticodon of tRNA with radioactive guanine (N. Okada and S. Nishimura, unpublished data). tRNA isolated from various tumors, including slowly growing Morris hepatoma 7794A, incorporated considerable guanine with E. coli guanine insertion enzyme, whereas tRNA isolated from all normal tissues so far tested, except regenerating rat liver, incororated scarcely any. In the rat ascites hepatoma AH7974, the guanine was mostly incorporated into minor isoaccepting species of tRNA^sP that contained the guanine residue instead of Q base in the first position of the anticodon. This is a sensitive and easy method for identifying unique tRNA species in tumor tissues.Many new isoaccepting tRNA species have been found in particular tissues, cells at various stages of differentiation, tumor tissues, transformed cells, and cells grown under different culture conditions (for reviews, see refs. 1-3). Various techniques have been used in attempts to detect unique tRNA species in tumor cells, and it has been found that the amount of methylated nucleosides in tRNA and the activities of tRNA methylases are generally high in tumor tissues (3, 4). However, analyses of modified nucleosides using total unfractionated tRNA have given results dependent upon the tumor tissues examined (5). Recently, Kuchino and Borek (6) demonstrated that the tRNAPhe that specifically appeared in Novikoff hepatoma and Ehrlich ascites tumor cells contains 1-methylguanine, unlike tRNAPhe in normal tissues. The new tRNAPhe species that appears in some tumor tissues is due to lack of modified base Y in the position next to the anticodon (7,8). A new isoaccepting species of tRNA has often been detected in tumor cells by analyzing changes in the chromatographic profile of amino acid acceptor activity (3). However, new tRNA cannot always be detected in this way because the elution position of tRNA may be influenced by several factors. In addition, most methods used previously require a large quantity of material and pure species of tRNA, which are difficult to obtain from tumor tissues.In this paper, we report a method for detecting unique tRNA species specifically present in tumor cells. We previously reported that the guanine insertion enzyme from rabbit reticulocytes, discovered by Farkas (9), specifically catalyzes the exchange of modified base Q in Escherichia coli tRNA with guanine without breaking the polynucleotide chain (10). A guanine insertion enzyme has also been found in other organisms, such as E. coli (N. Okada and S. Nishimura, unpublished data) and Ehrlich ascites tumor cells (11), and an extensively purified preparation from E. coli catalyzed exchange of guanine with guanine, but not of Q base in tRNA with guanine (N.The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fac...

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Atypical Transfer RNA's And Their Origin In Neoplastic Cells

Cited by 171 publications

References 73 publications

Clinical significance and prognostic value of urinary nucleosides in breast cancer patients

Clinical significance and prognostic value of urinary nucleosides in breast cancer patients

S-Adenosylhomocysteine inhibition of three purified tRNA methyltransferases from rat liver

Detection of unique tRNA species in tumor tissues by Escherichia coli guanine insertion enzyme.

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