期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 275, 期 32, 页码 24407-24413出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M909771199
关键词
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We previously identified a constitutively active form of STAT (signal transducer and activator of transcription) 5A by polymerase chain reaction-driven random mutagenesis followed by retrovirus-mediated expression screening, which had two point mutations in the DNA-binding and transcriptional activation domains, and was designated STAT5A1*6, STAT5A1*6 showed markedly elevated DNA binding and transactivation activities with stable tyrosine phosphorylation and nuclear accumulation, and conferred autonomous cell growth on interleukin 3-dependent Ba/F3 cells. We now report another constitutively active mutant, STAT5A-N642H which has a single point mutation (N642H) in its SH2 domain, identified using the same strategy as that used to identify STAT5A1*G, STAT5A-N642H showed identical properties to those of STAT5A1*6 both biochemically and biologically. Interestingly the mutation in STAT5A-N642H resulted in restoration of the conserved critical histidine which is involved in the binding of phosphotyrosine in the majority of SH2-containing proteins. Introduction of an additional mutation (Y694F) to STAT5A-N642H, which disrupted critical tyrosine 694 required for dimerization of STATE, abolished all the activities manifested by the mutant STAT5A-N642H, which indicates that dimerization is required for the activity of STAT5A-N642H as was the case for the wild-type STAT5A The present findings also show that different mutations rendered STAT5A constitutively active, through a common mechanism, which is similar to that of physiological activation.
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