ISOTOPE PROGRAM.  Final Report

Nathans, M.W.

doi:10.2172/4588880

Cited by 6 publications

(10 citation statements)

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“…Low phosphate medium used for "P 312 labelling, phage infection, extraction of 32 P-labelled RNA, and electrophoresis on polyacrylamide slab gel were also described earlier [5]. A dialyzed S30 preparation of E. coli, used for the in vitro cleaving reactions of precursor tRNA molecules, was prepared as described by Nathans [6]. Fingerprint analysis of Tl-ribonuclease digests of RNA was performed according to the method described by Barrel1 [ 71.…”

Section: Methodsmentioning

confidence: 99%

Studies on T4‐tRNA biosynthesis: Accumulation of precursor tRNA molecules in a temperature sensitive mutant of Escherichia coli

1974

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Section: Methodsmentioning

confidence: 99%

Studies on T4‐tRNA biosynthesis: Accumulation of precursor tRNA molecules in a temperature sensitive mutant of Escherichia coli

1974

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“…Dialyzed S30 extracts were prepared as described by Nathans (11). Unless otherwise noted, the reaction mixture contained 10 mM Tris HCl (pH 7.8), 100 gM EDTA, 5 mM Mg9l2, 100 ,M 2-mercaptoethanol, and Yo volume of S30.…”

Section: Methodsmentioning

confidence: 99%

Sequential processing of precursor tRNA molecules in Escherichia coli.

Sakano¹,

Shimura²

1975

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

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In a temperature-sensitive mutant of E. cofl defective in tRNA biosynthesis, many tRNA precursors, including monomeric and multimeric forms, accumulate. Some of the multimeric precursors contain three or more tRNA seuences within a molecule. These large precursors were cleaved by cell extracts first into intermediate size pieces which were subsequently processed by RNase P. On the basis of heat stability of mutant cell extracts, the endonuclease responsible for the initial cleavage appears to be distinct from RNase P and is designated RNase 0. One of the monomeric precursors was shown to be processed first by RNase P and the product subsequently cleaved further into a smaller molecule. The nuclease responsible for this second cleavage also appears to be distinct rom RNase P and is designated RNase Q. The functions of these nucleases are sequential in the trimming process with respect to that of RNase P; RNase 0 works prior to RNase P and RNase Q after RNase P but in both cases, not vice versa. The notion that tRNAs are formed from the initial transcripts of tRNA genes via a series of processing steps has been well accepted (1). These initial precursors are expected to be larger than mature tRNA size. Thus, the precursor molecules must be cleaved at specific sites in the maturation process. In the case of Su3+ suppressor tRNA, an unmodified precursor RNA carrying additional nucleotides at both the 5' and 3' termini has been detected (2, 3), and an endonuclease that cleaves this precursor at the 5' end of Su3+ tRNA has been identified in Escherichia coli extract and designated RNase P (4). Temperature-sensitive mutants of E. coli defective in this nucleolytic activity have been reported (5-7). So far, this is the only nuclease that has been clearly shown to participate in the trimming process of E. colh. It is anticipated, however, that some other nucleases are also required in maturation of tRNA molecules. Although a few other candidates have been suggested (1), none of them has been as firmly established as RNase P. Thus it remains to be solved how many nucleolytic enzymes participate in the processing of E. coli tRNAs and how they work during the trimming process. In the present paper we report that there are at least two other nucleases in E. coil that are required for tRNA biosynthesis. Evidence will be presented showing that these two nucleases and RNase P function in a highly ordered fashion on the precursors of E. coli tRNA molecules. MATERIALS AND METHODSBacterial Strains. E. coli 4273 (su, lacam, T6amr, BF23amr) and TS241, a temperature-sensitive mutant of 4273, defective in tRNA biosynthesis were described previously (6). E. colh Q13 (RNase I-) was originally from Dr. R. F. Gesteland.Preparation of RNA and Polyacrylamide Gel Electrophoresis. Low phosphate medium used for 32p labeling and extraction of RNA were described earlier (6). Electrophoresis in 10% or 12% polyacrylamide gel was performed in 0.1 M Tris-acetate (pH 8.3) as described by DeWachter and Fiers (9). 20% polyacrylamide gel was pre...

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“…For example, the list of the types and amounts of isotopes added to the device for the production study is classified, though it is known that the most significant isotope was tritium (Gardner and Sigalove, 1970). Although no information is given for other radionuclides, Nathans (1965) reports that 0.06 g of tritium were placed in the zero room, equivalent to about 6.0 x 1014 pCi. The amount (if any) of unburned nuclear fuel (including isotopes of Pu, U, and H) remains classified as well.…”

Section: Source Termsmentioning

confidence: 99%

“…No detailed radionuclide inventory of this material has been found, but as it presumably originated from the Gnome shot, it is most likely accounted for in Table 2. In the case of tritium, the 6.0 x 1014 pCi placed in the zero room (Nathans, 1965) was added to the 1.1 x 1014 pCi reported by Gardner and Sigalove (1970) to obtain the value given in Table 2.…”

Section: Source Termsmentioning

confidence: 99%

“…For example, most postshot surveys conducted by re-entering the Gnome cavity after the shot found the majority of the radionuclides confined to melt (or glass) zones at the base of the cavity (Rawson etaZ., 1965). Studies of this material revealed that almost all of the fission products remained with the salt impurities when samples were dissolved in water or remelted to separate the NaCl (Rawson et aZ., 1965, Nathans, 1965. Those nuclides that do leach slowly out of melt debris often have strong sorbing properties that also limit migration.…”

Section: Source Termsmentioning

confidence: 99%

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