Appearance of CAD activity, the rate-limiting enzyme for pyrimidine biosynthesis, as B cells progress into and through the G1 stage of the cell cycle.
CAD is a multifunctional protein which mediates the first three enzymatic steps of pyrimidine biosynthesis. Previous studies have implicated CAD as a cell cycle regulated protein. In the present paper CAD activity is studied as polyclonally stimulated, murine B cells progress through the early stages of the cell cycle. CAD activity is seen to increase in a biphasic manner. The initial increase in activity occurs prior to or as the cells increase CAD mRNA suggesting that post-translational modification of preformed enzyme may account for at least a portion of this initial enhancement. Increases in CAD mRNA occur by 12 hr poststimulation and precede the second, more dramatic increase in B cell CAD activity. Preliminary experiments failed to provide support of a role for IL-4 in regulating the expression of CAD as B cells progress into G1. CAD enzymatic activity does represent, however, a marker for early B cell cycle progression.
Morford
G
G
Department of Microbiology and Immunology, University of Kentucky Medical Center, Lexington 40536-0084.
Davidson
J N
JN
Snow
E C
EC
D000818:Animals; D001221:Aspartate Carbamoyltransferase / Q000235:genetics / Q000378:metabolism*; D001402:B-Lymphocytes / Q000166:cytology / Q000201:enzymology*; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004080:Dihydroorotase / Q000235:genetics / Q000378:metabolism*; D016193:G1 Phase; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D011743:Pyrimidines / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000235:genetics
C033626:CAD trifunctional enzyme; D009097:Multienzyme Complexes; D011743:Pyrimidines; D012333:RNA, Messenger; D004247:DNA; D001221:Aspartate Carbamoyltransferase; D004080:Dihydroorotase; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing)