Dephosphorylation of "abp38" protein during the differentiation of mouse myeloid leukemia cells

We have characterized the phosphorylation of "abp38" before and after the differentiation of mouse myeloid leukemic cells (M1 cells). The abp38 of both undifferentiated and differentiated M1 cells contained phosphoserine and phosphotyrosine. The extent of phosphorylation of abp38 decreased to about 30% of the value of undifferentiated cells during cell differentiation; phosphoserine and phosphotyrosine decreased to 41 and 11% of the values before differentiation, respectively.