Products of the TAL1 oncogene: basic helix-loop-helix proteins phosphorylated at serine residues
Cheng, J.T.; Hsu, H.L.; Hwang, L.Y.; Baer, R.
Oncogene 8(3): 677-683
1993
ISSN/ISBN: 0950-9232 PMID: 8437851 Document Number: 416764
TAL1 gene rearrangement is observed in nearly 30% of patients with T-cell acute lymphoblastic leukemia (T-ALL), and thus it represents the most common genetic lesion associated with this disease. Nevertheless, the presence of TAL1 gene products in normal or leukemic cells has not been reported. Therefore, immunoprecipitation with anti-TAL1 antisera was used to demonstrate the presence of TAL1 phosphoproteins, pp42-TAL1 and pp22-TAL1, in both T-ALL and erythroleukemia cell lines. The pp42-TAL1 and pp22-TAL1 proteins appear to be phosphorylated forms of full-length and truncated TAL1 gene products respectively. Phosphoamino acid analysis revealed that pp42-TAL1 contains phosphoserine residues. The TAL1 phosphoproteins were detected in all of the T-ALL cell lines that harbor obvious TAL1 gene rearrangements. Interestingly, pp42-TAL1 and pp22-TAL1 were also present in some, but not all, of the T-ALL lines without detectable TAL1 gene alterations. Therefore, TAL1 activation may promote leukemogenesis in a far greater proportion of T-ALL patients than the 30% that bear gross TAL1 gene arrangements.