Thioredoxin is required for deoxyribonucleotide pool maintenance during S phase.
Thioredoxin was initially identified by its ability to serve as an electron donor for ribonucleotide reductase in vitro. Whether it serves a similar function in vivo is unclear. In Saccharomyces cerevisiae, it was previously shown that Deltatrx1 Deltatrx2 mutants lacking the two genes for cytosolic thioredoxin have a slower growth rate because of a longer S phase, but the basis for S phase elongation was not identified. The hypothesis that S phase protraction was due to inefficient dNTP synthesis was investigated by measuring dNTP levels in asynchronous and synchronized wild-type and Deltatrx1 Deltatrx2 yeast. In contrast to wild-type cells, Deltatrx1 Deltatrx2 cells were unable to accumulate or maintain high levels of dNTPs when alpha-factor- or cdc15-arrested cells were allowed to reenter the cell cycle. At 80 min after release, when the fraction of cells in S phase was maximal, the dNTP pools in Deltatrx1 Deltatrx2 cells were 60% that of wild-type cells. The data suggest that, in the absence of thioredoxin, cells cannot support the high rate of dNTP synthesis required for efficient DNA synthesis during S phase. The results constitute in vivo evidence for thioredoxin being a physiologically relevant electron donor for ribonucleotide reductase during DNA precursor synthesis.
Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, USA.
Ahmet
A
Koc
Christopher K
CK
Mathews
Linda J
LJ
Wheeler
Michael K
MK
Gross
Gary F
GF
Merrill
D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D003854:Deoxyribonucleotides / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D005800:Genes, Fungal; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D054464:Peroxiredoxins; D012264:Ribonucleotide Reductases / Q000378:metabolism; D016196:S Phase / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism*
C082279:CDC15 protein; D018797:Cell Cycle Proteins; D003854:Deoxyribonucleotides; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; C103243:TRX1 protein, S cerevisiae; C516110:TRX2 protein, S cerevisiae; D013879:Thioredoxins; D054464:Peroxiredoxins; D012264:Ribonucleotide Reductases; D019204:GTP-Binding Proteins