Up-regulation of small GTP-binding proteins smg P21A and ras P21S during TPA-induced differentiation of human leukemia cell lines

Abstract

The protein smg p21A/K rev-1/ rap 1A was identified as a ras p21-like small G-protein, having the ability to revert v-Ki- ras transformed NIH 3T3 fibroblasts. The expression level of smg p21A and ras p21s during phorbol ester-induced differentiation of HL-60 and MEG-01 cell lines was analyzed by immuno- and Northern blotting. In both cell lines, levels of smg p21 and ras p21s increased quickly in early phase of differentiation along with the appearance of differentiation phenotypes. They increased 3–4 fold on days 1–2, then decreased gradually. The increasing smg 21 mRNA levels also corresponded with that of products. Among ras mRNAs, Ha- ras and N- ras transcripts increased somewhat faster than smg 21. These small G-proteins may play closely related roles in the differentiation of these leukemia cell lines.