NUCLEOTIDE-SEQUENCE OF 3 ISOACCEPTING LYSINE TRANSFER-RNAS FROM RABBIT LIVER AND SV40-TRANSFORMED MOUSE FIBROBLASTS
NUCLEOTIDE-SEQUENCE OF 3 ISOACCEPTING LYSINE TRANSFER-RNAS FROM RABBIT LIVER AND SV40-TRANSFORMED MOUSE FIBROBLASTS
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DOI：
10.1111/j.1432-1033.1979.tb13115.x
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发表时间：
1979-01-01
期刊：
影响因子：
--
通讯作者：
GROSS, HJ
中科院分区：
文献类型：
--
作者：
RABA, M;LIMBURG, K;GROSS, HJ
The Lys isoacceptor tRNA differ in 2 aspects from the majority of the other mammalian tRNA species: they do not contain ribosylthymine (T) in loop IV, and a new Lys tRNA, which is practically absent in non-dividing tissue, appears at elevated levels in proliferating cells. The 3 major isoaccepting Lys tRNA from rabbit liver and the new Lys tRNA isolated from SV40-transformed mouse fibroblasts were purified and their nucleotide sequences were determined. The 3 major Lys tRNA (species 1, 2 and 3) from rabbit liver contain 2''-O-methyl-ribosylthymine (Tm) in place of T .**GRAPHIC**. and .**GRAPHIC**. differ only by a single base pair in the middle of the anticodon stem; the anticodon sequence C-U-U [C = cytosine, U = uracil] is followed by N-threonyl-adenosine (t6A). .**GRAPHIC**. has the anticodon S-U-U and contains 2 highly modified thionucleosides, S (shown to be 2-thio-5-carboxymethyl-uridine methyl ester) and a further modified derivative of t6A (2-methyl-thio-N6-threonyl-adenosine) on the 3'' side of the anticodon. .**GRAPHIC**. differs in 14 and 16 positions, respectively, from the other 2 isoacceptors. Protein synthesis in vitro, using synthetic polynucleotides of defined sequence, showed that .**GRAPHIC**. with anticodon C-U-U recognized A-A-G [A = adenine, G = guanine] only, whereas .**GRAPHIC**. which contains thionucleotides in and next to the anticodon, decodes both Lys codons A-A-G and A-A-A, but with a preference for A-A-A. In a globin-mRNA-translating cell-free system from ascites cells, both Lys tRNA donated Lys into globin. The rate and extent of Lys incorporation was higher with .**GRAPHIC**. than with .**GRAPHIC**. in agreement with the fact that .alpha.-globin and .beta.-globin mRNA contain more A-A-G than A-A-A codons for Lys. A comparison of the nucleotide sequences of Lys tRNA species 1, 2 and 3 from rabbit liver, with that of the new .**GRAPHIC**. from transformed and rapidly dividing cells showed that this tRNA is not the product of a new gene or group of genes, but is an undermodified tRNA derived exclusively from .**GRAPHIC**. Of the 2 dihydrouridines present in .**GRAPHIC**. 1 is found as U in .**GRAPHIC**. the purine next to the anticodon is as yet unidentified but is known not to be t6A. U, T and .PSI. [pseudouridine] were also found besides Tm as the 1st nucleoside in loop IV.
