title: Retinoic acid alters subcellular compartmentalization of ATP pools in 3T3 cells but not in HeLa cells.
abstract: Retinoic acid (RA; beta-all-trans) inhibits the proliferation of both murine 3T3 cells and human HeLa cells. Flow cytometric analyses of exponentially growing cultures show that 3T3 cells are inhibited during the S phase of their cell cycle, while HeLa cells show only a small increase in G1 phase cells. RA (10 microM) causes a 50% increase in total cellular adenosine triphosphate (ATP) pools of 3T3 cells, but not of HeLa cells. We have previously demonstrated that the effects of RA on cellular ATP pools of 3T3 cells are directly related to its inhibition of cellular growth, and now report data which provide a biochemical basis for this process. Established procedures were utilized to investigate the effects of RA on the functional compartmentalization of the nuclear ATP pool which serves as a precursor for RNA synthesis in these cells, and which is shown to be a small pool in comparison with cytoplasmic ATP pools. Expansion of total cellular ATP pools by 1 mM of exogenously supplied unlabeled adenosine is ineffective in reducing the subsequent incorporation of [3H]adenosine into RNA of 3T3 cells. Similar treatment of HeLa cells yields a modest reduction in the incorporation of [3H]adenosine into RNA. RA treatment of HeLa cells does not affect the preferential uptake of exogenous [3H] adenosine into the immediate precursor ATP pool for RNA synthesis. RA treatment of 3T3 cells markedly reduces the incorporation of [3H] adenosine into RNA, indicating a lesser degree of functional compartmentalization of the nuclear ATP pool. Similar conclusions are drawn from correlations of the specific radioactivities of total cellular [3H] ATP pools and the levels of incorporation of radioactive label into cellular RNA. In addition, pulse-chase experiments show that RA-treated 3T3 cells continue to incorporate radioactive label from pools prelabeled with [3H]adenosine despite the presence of a large excess of unlabeled adenosine in the chase medium. Control 3T3 and both control and RA-treated HeLa cells cease to incorporate label immediately upon the start of the chase, suggesting that the functional precursor ATP pool for RNA synthesis is small and readily diluted. These data suggest that RA decreases the degree of functional compartmentalization for 3T3, but not HeLa cell ATP pools, and provides a probable mechanism for expansion of nuclear ATP pools of 3T3 cells. The expanded nuclear ATP pools may provide the biochemical mechanism for the inhibition of DNA synthesis during the S phase of the 3T3 cell cycle.
mesh_terms: D000241:Adenosine / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism*; D006367:HeLa Cells / Q000378:metabolism*; D006801:Humans; D007399:Interphase / Q000187:drug effects; D051379:Mice; D012313:RNA / Q000096:biosynthesis; D013347:Subcellular Fractions / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D014212:Tretinoin; D012313:RNA; D000255:Adenosine Triphosphate; D000241:Adenosine