Synthesis and biochemical characteristics of nucleoproteins following a toxic dose of retinoic acid in cycling and differentiating HL-60 cells.

ABSTRACT

Exposure of HL-60 cells to 2 microM retinoic acid (RA), twice the dose necessary for differentiation, initiated rapid synthesis (2 h) of the nuclear stress proteins (SPs) e.g., 90, 70c, 70x, 22 (Mr x 10(-3)) during the G0 + G1 phase of the cell cycle as observed by polyacrylamide gel electrophoresis (PAGE). Synthesis of SPs was cell cycle correlated and not dependent on time-after-dosing, and all labeling disappeared from these proteins within 48 h of RA exposure. Stress proteins were not elicited with a 1 microM dose or less of retinoic acid. Non-stress nuclear proteins revealed changes in synthesis levels (e.g., actin, lamins, tubulins) which were cell cycle related and temporally associated with dosing. A major non-stress nuclear protein (Mr 120,000) which possessed an affinity for actin in binding assays, was cell cycle related in control cells, and was suppressed in synthesis in cells exposed to 2 microM retinoic acid. Two additional nuclear non-SPs 51 and 55 (Mr x 10(-3)) covalently bound the isotope [3H]retinoic acid, and their incorporation was cell cycle correlated during early periods of RA exposure. Except for the induction of SPs, the autoradiographs of nuclear proteins of RA dosed HL-60 cells, showed more quantitative than qualitative changes.