DIFFERENTIAL PHOSPHORYLATION OF LAMIN B-2 IN NORMAL AND LEUKEMIC-CELLS

Lamins constitute the nuclear lamina, which underlie the inner membran e of the cell nucleus. Phosphorylation of lamins is a key factor in th e regulation of nuclear structure during the cell cycle and of gene tr anscription. Since an uncontrolled cell cycle and altered gene transcr iption are major characteristics of neoplasms, we looked for differenc es in lamin B-2 phosphorylation between PBMC, ALL and AML cells. Using different lamin B-2-specific antibodies, we detected two different la min B-2 species termed lamin B-2 and B-2A?. Although phosphorylation o f lamin B-2 in leukemic cells was reminiscent of resting cells, the ma jority of ALL and AML samples showed significantly higher and more alt ered lamin B-2A phosphorylation compared to PBMC. It remains to be elu cidated which mechanism leads to these alterations and whether it coul d explain the extended G(1)-phase frequently observed in ALL cells. (C ) 1997 Elsevier Science Ltd.