Biomedical subjects

V K Lin

Publications and source records attributed to V K Lin.

24 records · Page 2Linked to original sources

PubMed1983

Competence and progression growth factors stimulate different tRNAlys modification reactions in BALB/C 3T3 cells.

Sparse cultures of Balb/C 3T3 cells were growth arrested in a medium containing 1% calf plasma. This treatment caused a decrease in tRNA4lys, a tRNA species related to cell division, and a corresponding increase in tRNA5lys. A restoration of tRNA4lys levels and an increase in cell number was obtained by the addition of either 10% calf serum or a combination of fibroblast growth factor and melanocyte stimulating activity. Neither growth factor alone evoked a proliferative response. The progression factors, insulin and multiplication stimulating activity stimulated the rapid conversion of tRNA5lys to tRNA2lys, whereas the competence factors, fibroblast growth factor and platelet-derived growth factor stimulated a slight conversion of tRNA2lys to tRNA4lys.

Animals↗

PubMed1983

The effects of growth factors on tRNALys modification.

The tRNALys population from tissue culture cells contains several isoaccepting species which are not present in the tRNALys population from tissue sources. These isoacceptors were isolated from mouse LM cells and tested for their coding properties in ribosomal binding assays and their ability to incorporate lysine into protein in a reticulocyte lysate. tRNALys5A and tRNALys6 eluted in the area of tRNALys5. All three species coded preferentially for AAA and bound with equal efficiency. tRNALys1, tRNALys3, tRNALys4, and tRNALys6 all transferred lysine into protein at a slower rate than tRNALys2 and tRNALys5, which are the native species. Several purified growth factors were tested for their ability to affect the levels of tRNALys4, a tRNA possibly associated with cell division. When Balb/c 3T3 cells were grown in medium containing plasma instead of serum, there was a decrease in tRNALys2, tRNALys3, tRNALys4 and an increase in tRNALys5 and tRNALys6. The addition of either FGF or PDGF returned the tRNALys profile to normal. The extent of the tRNALys changes depended upon the concentration of growth factor added. FGF was able to cause a 35% decrease in the tRNALys5 peak with a corresponding increase in tRNALys2 within 1 h of the addition of the factor. These data suggest that competence factors have the ability to stimulate the modification of specific tRNALys isoacceptors.

Animals↗

PubMed1983

Perturbation of the mitochondrial lysine tRNA population by virus-induced transformation or stress of mammalian cells: functional properties and nucleotide sequence of a mitochondrially associated lysine tRNA.

Eleven isoaccepting lysine tRNAs from mammalian sources are demonstrable by RPC-5 chromatography and polyacrylamide gel electrophoresis. The appearance and amounts of these isoacceptors varies with the source and growth state of cells. One isoacceptor, tRNALys6, observed in preparations of tRNA from some virus-transformed cells in culture, has been characterized by determining functional properties, cellular location, and its nucleotide sequence. tRNALys6 responds primarily to the lysine codon AAA, but it is not used efficiently in a wheat germ translational system in vitro. Compared with lysine isoacceptors 1, 2, 4, 5a, and 5, [3H]lysine appears in vivo in tRNALys6 with a delay of about 3 h. This delay may in part be a result of a less functional tRNA, but a compartmented state of tRNALys6 also appears to be important. tRNALys6 is associated with mitoplasts prepared from KA31 fibroblasts. The nucleotide sequence of tRNALys6 was determined by rapid postlabeling procedures involving limited hydrolysis in formamide, 32P-labeling of 5' ends of fragments with polynucleotide kinase, separation of the nested set of fragments in polyacrylamide denaturing gels, release of 5'-labeled nucleotides with RNase T2, and identification of the released nucleotides by chromatography on PEI cellulose. Confirmation of the positions of major nucleotides was done by using limited digestions by RNases of tRNALys6 labeled with 32P on the 3' terminus in a gel readout procedure. The nucleotide sequence of tRNALys6 differs from that of cytoplasmic lysine tRNAs and mammalian mitochondrial lysine tRNAs. It contains U*, an unidentified modified uridine occurring in the anticodon of some mitochondrial tRNAs. tRNALys6 appears to occur in very limited amounts, or not at all, in most cells unless stressed, but when present it is associated with mitochondria, although it is probably coded in the nucleus.

Animals↗

PubMed1980

Alterations in tRNA isoaccepting species during erythroid differentiation of the Friend leukemia cell.

The chromatographic profiles of isoaccepting tRNAs were analyzed at five time points during the 96 hr, dimethylsulfoxide induced, erythroid-like differentiation of Friend leukemia cells. Sixty-four isoaccepting species of tRNA for 16 amino acids were resolved by RPC-5 chromatography. The relative amounts of tRNAphe, tRNAile, and tRNAval species were maintained by the cells during differentiation; whereas the relative amounts of some of the isoacceptor tRNAs for the other 13 amino acids changed significantly. Fluctuations in amounts of isoacceptors occurred between 36 and 72 hr after addition of dimethysulfoxide, corresponding to globin mRNA appearance and hemoglobin synthesis, respectively. In most cases, thepredominant tRNA isoacceptors of uninduced cells were retained throughout differentiation. Notable exceptions were tRNA species for threonine, proline, and methionine. Some of the isoacceptors occurring in relatively smaller amounts were not expressed at all times. These changes possibly reflect the cell's functional adaptation of tRNA in differentiation for hemoglobin synthesis.

Animals↗

PubMed1980

Specific changes in Q-ribonucleoside containing transfer RNA species during Friend leukemia cell erythroid differentiation.

Changes in specific tRNA isoacceptors during Friend leukemia cell (F.L.C.) erythroid differentiation have been found to be concomitant with differences in the extent of the Q-base modification in certain species of tRNA. Transfer RNA was isolated from F.L.C. cultures after 0, 36, 48, 72, and 96 hr of DMSO induced differentiation. Changes in 17 isoacceptors of tRNAasn, tRNAasp, tRNAhis and tRNAtyr were compared by RPC-5 chromatography. Isoacceptors of these tRNA changed in relative amounts, following consistent trends throughout cell differentiation. The amount and distribution of Q-base containing tRNA isoacceptors was assayed by measuring the quanine-tRNA transferase catalyzed incorporation of [3H]-labeled guanine into tRNA species undermodified in Q-base followed by RPC-5 chormatography of the tRNA. The amount of Q-base containing tRNA species decreased in the first 48 hr after the induction, then increased again, indicating the level of Q-modification is correlated to the process of differentiation. Isoacceptors that lacked the Q-base were eluted late from RPC-5.

Animals↗

PubMed1979

Transfer RNATyr of melanoma tissues and cells: relevance to melanin synthesis?

The tRNA present in swine melanoma tumor tissue and normal gray skin tissue were compared by aminoacylation of the unfractionated tRNA preparations. Of the seventeen amino acids studied, seven showed differences in rate of acceptance to tRNAs from normal and tumor tissues; the tRNAs of two amino acids, tyrosine and glycine, showed dramatic three fold increases in melanoma tumor. As melanin biosynthesis proceeds from tyrosine oxidation the investigations focused on the increase in tyrosine tRNA. Kinetic analysis of tyrosine aminoacylation to normal and melanoma tRNAs revealed no differences. Analysis of the isoaccepting species of tRNATyr from normal skin and melanoma tumor tissues identified three isoacceptors; tRNATyr, represented the predominant species in normal gray skin, while tRNA2Tyr predominated in melanoma tumor tissue. The tyrosine acceptances by tRNAs from three human melanoma cell lines were analyzed and found to be variable, but isoaccepting species analysis of the tRNATyr of these three cell lines still showed a correlation between the preponderance of tRNA2Tyr and extent of tyrosine acceptance. Additionally the enzymatic activity for the oxidation of tyrosine was found to be related to tyrosine acceptance and tRNA2Tyr predominance..

Amino Acyl-tRNA Synthetases↗