Reverse Methionine Biosynthesis fromS-Adenosylmethionine in Eukaryotic Cells*

The intracellular ratio between methionine and its activated form S-adenosylmethionine (AdoMet) is of crucial importance for the one-carbon metabolism. AdoMet recycling into methionine was believed to be largely achieved through the methyl and the thiomethyladenosine cycles. We show here that in yeast, AdoMet recycling actually occurs mainly through the direct AdoMet-dependent remethylation of homocysteine. Compelling evidences supporting this result were obtained owing to the identification and functional characterization of two new genes,SAM4 and MHT1, that encode the yeast AdoMet-homocysteine methyltransferase andS-methylmethionine-homocysteine methyltransferase, respectively. Homologs of the Sam4 and Mht1 proteins exist in other eucaryotes, indicating that such enzymes would be universal and not restricted to the bacterial or fungal kingdoms. New pathways for AdoMet or S-methylmethionine-dependent methionine synthesis are presented.

[1]  E. Burton,et al.  The substrate specificity of 5-methyltetrahydropteroyltriglutamate-homocysteine methyltransferase. , 1969, The Biochemical journal.

[2]  R. S. Muir,et al.  Gene disruption with PCR products in Saccharomyces cerevisiae. , 1995, Gene.

[3]  M. Donoviel,et al.  Isolation and identification of genes activating UAS2-dependent ADH2 expression in Saccharomyces cerevisiae. , 1996, Genetics.

[4]  A. Böck,et al.  A Family of S-Methylmethionine-dependent Thiol/Selenol Methyltransferases , 1999, The Journal of Biological Chemistry.

[5]  F. Nieto,et al.  The effects of folic acid supplementation on plasma total homocysteine are modulated by multivitamin use and methylenetetrahydrofolate reductase genotypes. , 1997, Arteriosclerosis, thrombosis, and vascular biology.

[6]  C. Hodgson,et al.  Hybridization probe size control: optimized 'oligolabelling'. , 1987, Nucleic acids research.

[7]  H. Mountain,et al.  Four major transcriptional responses in the methionine/threonine biosynthetic pathway of Saccharomyces cerevisiae , 1991, Yeast.

[8]  A. Hanson,et al.  Characterization and Functional Expression of cDNAs Encoding Methionine-sensitive and -insensitive Homocysteine S-Methyltransferases from Arabidopsis * , 2000, The Journal of Biological Chemistry.

[9]  K. Cornell,et al.  Affinity purification of 5-methylthioribose kinase and 5-methylthioadenosine/S-adenosylhomocysteine nucleosidase from Klebsiella pneumoniae [corrected]. , 1996, The Biochemical journal.

[10]  R. Smith,et al.  5'-Methylthioadenosine metabolism and methionine synthesis in mammalian cells grown in culture. , 1982, Biochemical and biophysical research communications.

[11]  R. Sikorski,et al.  A system of shuttle vectors and yeast host strains designed for efficient manipulation of DNA in Saccharomyces cerevisiae. , 1989, Genetics.

[12]  D G Higgins,et al.  CLUSTAL V: multiple alignment of DNA and protein sequences. , 1994, Methods in molecular biology.

[13]  H. Cherest,et al.  Two divergent MET10 genes, one from Saccharomyces cerevisiae and one from Saccharomyces carlsbergensis, encode the alpha subunit of sulfite reductase and specify potential binding sites for FAD and NADPH , 1994, Journal of bacteriology.

[14]  Y. Surdin-Kerjan,et al.  SAM2 encodes the second methionine S-adenosyl transferase in Saccharomyces cerevisiae: physiology and regulation of both enzymes , 1988, Molecular and cellular biology.

[15]  Gerald R. Fink,et al.  Methods in Yeast Genetics: Laboratory Manual , 1981 .

[16]  A. Hanson,et al.  Salinity promotes accumulation of 3-dimethylsulfoniopropionate and its precursor S-methylmethionine in chloroplasts. , 1998, Plant physiology.

[17]  Y. Surdin-Kerjan,et al.  Transport of Sulfonium Compounds , 1999, The Journal of Biological Chemistry.

[18]  P. Thomas,et al.  Hybridization of denatured RNA and small DNA fragments transferred to nitrocellulose. , 1980, Proceedings of the National Academy of Sciences of the United States of America.

[19]  R. Smith,et al.  Methionine synthesis from 5'-methylthioadenosine in rat liver. , 1981, The Journal of biological chemistry.

[20]  M. Tyers,et al.  Feedback‐regulated degradation of the transcriptional activator Met4 is triggered by the SCFMet30 complex , 2000, The EMBO journal.

[21]  T. A. Brown,et al.  A rapid and simple method for preparation of RNA from Saccharomyces cerevisiae. , 1990, Nucleic acids research.

[22]  M. Jacquet,et al.  Intergenic flip flop, a method for systematic gene disruption and cloning in yeast , 1996, Yeast.

[23]  S. Schold,et al.  Effect of long-term depletion of plasma methionine on the growth and survival of human brain tumor xenografts in athymic mice. , 1997, Nutrition and cancer.

[24]  F. Csaikl,et al.  Molecular cloning and characterization of the MET6 gene of Saccharomyces cerevisiae. , 1986, Gene.

[25]  R. Hoffman,et al.  Methionine-depletion modulates the efficacy of 5-fluorouracil in human gastric cancer in nude mice. , 1997, Anticancer research.

[26]  Mudd Sh,et al.  The S-Methylmethionine Cycle in Lemna paucicostata , 1990 .

[27]  R. Schiestl,et al.  Improved method for high efficiency transformation of intact yeast cells. , 1992, Nucleic acids research.

[28]  Y. Surdin-Kerjan,et al.  Genetic analysis of a new mutation conferring cysteine auxotrophy in Saccharomyces cerevisiae: updating of the sulfur metabolism pathway. , 1992, Genetics.

[29]  S. Phillips,et al.  Regulation of methionine biosynthesis in the Enterobacteriaceae. , 1991, Progress in biophysics and molecular biology.