Nuclear envelope and chromatin compositional differences comparing undifferentiated and retinoic acid- and phorbol ester-treated HL-60 cells

The human leukemic cell line (HL-60) can be induced to differentiate in vit ro to granulocytic form with retinoic acid (RA), or to monocytic/macrophage form with phorbol ester (TPA). The granulocytic form acquires nuclear lobu lation, nuclear envelope-limited chromatin sheets (ELCS), and cytoskeletal polarization, none of which are acquired following treatment with TPA. Immu noblotting analyses and capillary zone electrophoresis demonstrated that fo llowing RA treatment: lamins A/C and B1, and vimentin decreased to negligib le amounts; LAP2 beta, lamin B2 and emerin remained essentially unchanged; lamin B receptor (LBR) increased markedly; histone subtypes H1.4 and 1.5 ex hibited dephosphorylation. Following TPA treatment: lamins A/C and B1, B2 a nd vimentin increased in amount; LAP2 beta and emerin remained essentially unchanged; LBR increased markedly; histone subtypes H1.4 and 1.5 exhibited dephosphorylation. Emerin, which was cytoplasmic in undifferentiated or gra nulocytic cells, localized into the nuclear envelope following TPA. Normal human granulocytes revealed compositional differences compared to granulocy tic forms of HL-60, namely increased vimentin and appearance of histone sub type H1.3. A working hypothesis for nuclear lobulation postulates a combina tion of. increased nuclear envelope deformability due to lamins A/C and B1 deficiency; an increase in nuclear surface area/volume; an increase in chro matin-nuclear envelope interactions. (C) 2001 Academic Press.