Cell cycle regulation of the glyceraldehyde3phosphate dehydrogenaseluracil DNA glycosylase gene in normal human cells

Abstract

The cell cycle regulatlon of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH)/uracil DNA glycosylase (UDG) gene was examined in normal human cells. Steady state RNA levels were monitored by Northern blot analysis uslng a plasmid (pChug 20.1) whlch contained the 1.3 kb GAPDH/UDG cDNA. The blosynthesls of the 37 kDa GAPDH/UDG protein was determined using an anti-human placental GAPDH/UDG monoclonal antibody to lmmunopreclpltate the radiolabeled protein. Increases in steady state GAPDHAJDG mRNA levels were cell cycle specific. A blphaslc pattern was observed resulting In a 19 fold increase In the amount of GAPDHIUDG mRNA. The blosynthesls of the 37 kDa GAPDH/UDG protein displayed a similar blphasic regulation with a 7-fold increase. Pulse-chase experiments revealed a remarkably short half life of less than 1 hr. for the newly synthesized 37 kDa proteln, comparable to that previously documented for a number of oncogenes. GAPDH/UDG mRNA levels were markedly reduced at 24 hr. when DNA synthesis was maxlmal. These results define the GAPDH/UDG gene as cell cycle regulated with a characteristic temporal sequence of expression in relation to DNA synthesis. The cell cycle synthesis of a labile 37 kDa monomer suggests a possible regulatory function for this muitidimensional protein. Further, modulation of the GAPDH/UDG gene in the cell cycle may preclude its use as a reporter gene when the proliferative state of the cell is not kept constant. © 1993 Oxford University Press.