Frequency of replication/transcription errors in (A)/(T) runs of human genes.
To estimate the error rate of the gene expression machinery and its possible age-related increase, we compared the occurrence of polymerase errors during replication and transcription in (A)/(T) runs, in DNA and RNA of young and old individuals and of early- and late-passage cultured fibroblasts. We analyzed three human genes: TPRD, TGFBR2, and ATRX containing stretches of (A)8, (A)10, and (T)13, respectively. The error rate was determined by sequencing 100 cloned PCR or RT-PCR fragments from each DNA and RNA sample. The error rates in replication and transcription increased with the stretch length. The pooled error rates for genomic DNA were: TPRD (A)8, TGFBR2 (A)10, and ATRX (T)13: 1%+/-0.41, 15.8%+/-1.3, and 31.3%+/-2.9, while those for RNA were: 3.8%+/-0.5, 19.3%+/-2.1, and 54.3%+/-1.8, respectively. The deletions of one nucleotide were the most frequent errors. In the replication analysis, a significant difference was found in old versus young individuals for the ATRX (T)13. In the transcription analysis, significantly higher error rates were obtained in old versus young individuals for the TPRD (A)8 and TGFBR2 (A)10. For these genes, the error rate in RNA isolated from fibroblasts was significantly higher than that in blood. The data show a trend of age-related increase in replication/transcription errors; however further studies are necessary to confirm this hypothesis, since the sample size is small. This imperfect fidelity of the gene expression process may explain the evolutionary disadvantage of nucleotide repeats within coding sequences, and that these repeats are targets for mutations in human diseases.
Paoloni-Giacobino
A
A
Division of Medical Genetics, University of Geneva Medical School, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland.
Rossier
C
C
Papasavvas
M P
MP
Antonarakis
S E
SE
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000235:genetics*; D001483:Base Sequence; D002460:Cell Line; D004247:DNA / Q000235:genetics; D004249:DNA Damage; D004265:DNA Helicases; D017931:DNA Primers / Q000235:genetics; D004261:DNA Replication / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D005260:Female; D015894:Genome, Human; D006801:Humans; D009154:Mutation; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D011506:Proteins / Q000235:genetics; D012313:RNA / Q000235:genetics; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic; D000075924:X-linked Nuclear Protein
D017931:DNA Primers; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011506:Proteins; D018125:Receptors, Transforming Growth Factor beta; D014157:Transcription Factors; D012313:RNA; D004247:DNA; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D004265:DNA Helicases; C092332:ATRX protein, human; D000075924:X-linked Nuclear Protein