Residual ataxia telangiectasia mutated protein function in cells from ataxia telangiectasia patients, with 5762ins137 and 7271T-->G mutations, showing a less severe phenotype.
We have assessed several ataxia Telangiectasia mutated (ATM)-dependent functions in cells derived from ataxia telangiectasia patients, carrying either an ATM 5762ins137 splice site or a 7271T-->G missense mutation, with a less severe phenotype compared with the classical disorder. ATM kinase in vitro, from 5762ins137 cells, showed the same specific activity as ATM in normal cells, but the protein was present at low levels. In contrast, mutant ATM kinase activity in the 7271T-->G cells was only about 6% that of the activity in normal cells, although the level of mutant protein expressed was similar to normal cells. Phosphorylation of the DNA double strand break repair proteins Nbs1 and hMre11, following DNA damage, was observed in normal and 7271T-->G cells but was almost absent in both 5762ins137 and classical ataxia telangiectasia cells. The kinetics of p53 response was intermediate between normal and classical ataxia telangiectasia cells in both the 7271T-->G and 5762ins137 cells, but interestingly, c-Jun kinase activation following DNA damage was equally deficient in cell lines derived from all the ataxia telangiectasia patients. Our results indicate that levels of ATM kinase activity, but not induction of p53 or c-Jun kinase activity, in these cells correlate with the degree of neurological disorder in the patients.
Stewart
G S
GS
CRC Institute for Cancer Studies, the University of Birmingham, Vincent Drive, Edgbaston, Birmingham B15 2TT, United Kingdom.
Last
J I
JI
Stankovic
T
T
Haites
N
N
Kidd
A M
AM
Byrd
P J
PJ
Taylor
A M
AM
D001260:Ataxia Telangiectasia / Q000235:genetics*; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins; D002460:Cell Line; D002478:Cells, Cultured; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins; D004789:Enzyme Activation; D017353:Gene Deletion; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D015151:Immunoblotting; D048031:JNK Mitogen-Activated Protein Kinases; D007700:Kinetics; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009154:Mutation; D009687:Nuclear Proteins; D010641:Phenotype; D010766:Phosphorylation; D017354:Point Mutation; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D011839:Radiation, Ionizing; D012694:Serine / Q000378:metabolism; D013997:Time Factors; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D012694:Serine; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)