Altered p21-promoter binding in a subset of leukemia cell extracts. (A) Protein extracts were prepared from five random frozen samples of leukemic blasts from peripheral blood of patients presenting acutely with AML, and binding to the p21-promoter was determined on gel shift. Differences in the presence and in the mobility of binding complexes are evident. The slowly migrating band in extract from patient no. 5 is specific and competed by cold fragment. A short exposure is shown. HL-60 and CD34 extracts are loaded for comparison. Equal amounts of protein are used in each binding reaction. FAB and FACS analysis results of the samples are also shown. (B) Northern blot demonstrates variable expression of p21 message in the leukemic samples.