These studies in HL-60 cells examined the regulation of folylpolyglutamate synthetase (FPGS) activity at the level of gene expression during terminal maturation. Following addition of 210 mM MeSO to cultures of HL-60 cells at a concentration that induces maturation of 85-90% of the cells, FPGS activity, but not folylpolyglutamate hydrolase (FPGH) activity, was reduced 2-7-fold within 1-5 days. The initial decline in FPGS activity preceded any effect of MeSO on rate of growth and the increase in appearance of nitro blue tetrazoliumpositive cells, a marker of cellular maturation, and the decrease after 5 days of exposure to MeSO was solely accounted for by a 7-fold decrease in value for V. The same time and concentration dependence for MeSO was shown for the decline in FPGS activity, increase in nitro blue tetrazolium-positive cells, and decline in the level of a 2.1-kilobase FPGS mRNA during exposure to this inducer. This decline in FPGS mRNA was reversible when MeSO was removed from the culture medium but only until that time when an appreciable number of cells were committed to terminal maturation. Following growth of HL-60 cells with [H]MTX, used as a model folate compound, a large reduction in its intracellular polyglutamate pools was shown during maturation which quantitatively reflected the decline in FPGS activity as well as folate transport inward (Sirotnak, F. M., Jacobson, D. M., and Yang, C-H.(1986) J. Biol. Chem. 261, 11150-11156). Other data showed that folate status or obviation of the folate requirement during growth of these cells strongly influenced the rapidity of the onset of maturation following exposure to inducer. Overall, these results show that FPGS activity in HL-60 cells is a marker for proliferative capacity and that the underlying basis for the decline in FPGS activity during maturation is altered cognate gene expression which is manifested as early reversible and late irreversible phases. They also suggest that the coordinate reduction observed in folate transport, FPGS activity, dihydrofolate reductase, and probably other folate related enzymes by limiting macromolecular biosynthesis may be early programmed events in the maturation process that influence the switch from proliferation to senescence in these cells.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				E. Odin, Y. Wettergren, S. Nilsson, R. Willen, G. Carlsson, C. P. Spears, L. Larsson, and B. Gustavsson Altered Gene Expression of Folate Enzymes in Adjacent Mucosa Is Associated with Outcome of Colorectal Cancer Patients Clin. Cancer Res., December 1, 2003; 9(16): 6012 - 6019. [Abstract] [Full Text] [PDF]

				K. A. Zanetti and P. J. Stover Pyridoxal Phosphate Inhibits Dynamic Subunit Interchange among Serine Hydroxymethyltransferase Tetramers J. Biol. Chem., March 14, 2003; 278(12): 10142 - 10149. [Abstract] [Full Text] [PDF]

				G. J. Leclerc and J. C. Barredo Folylpoly-{{gamma}}-glutamate Synthetase Gene mRNA Splice Variants and Protein Expression in Primary Human Leukemia Cells, Cell Lines, and Normal Human Tissues Clin. Cancer Res., April 1, 2001; 7(4): 942 - 951. [Abstract] [Full Text]

				M. Aghi, C. M. Kramm, and X. O. Breakefield Folylpolyglutamyl Synthetase Gene Transfer and Glioma Antifolate Sensitivity in Culture and In Vivo J Natl Cancer Inst, July 21, 1999; 91(14): 1233 - 1241. [Abstract] [Full Text] [PDF]

				S. J. Freemantle and R. G. Moran Transcription of the Human Folylpoly-gamma -glutamate Synthetase Gene J. Biol. Chem., October 3, 1997; 272(40): 25373 - 25379. [Abstract] [Full Text] [PDF]

				K. Roy, K. Mitsugi, and F. M. Sirotnak Additional Organizational Features of the Murine Folylpolyglutamate Synthetase Gene. TWO REMOTELY SITUATED EXONS ENCODING AN ALTERNATE 5prime END AND PROXIMAL OPEN READING FRAME UNDER THE CONTROL OF A SECOND PROMOTER J. Biol. Chem., February 28, 1997; 272(9): 5587 - 5593. [Abstract] [Full Text] [PDF]

				K. Roy, K. Mitsugi, and F. M. Sirotnak Organization and Alternate Splicing of the Murine Folylpolyglutamate Synthetase Gene. DIFFERENT SPLICE VARIANTS IN L1210 CELLS ENCODE MITOCHONDRIAL OR CYTOSOLIC FORMS OF THE ENZYME J. Biol. Chem., September 27, 1996; 271(39): 23820 - 23827. [Abstract] [Full Text] [PDF]

				L. Chen, H. Qi, J. Korenberg, T. A. Garrow, Y.-J. Choi, and B. Shane Purification and Properties of Human Cytosolic Folylpoly-gamma -glutamate Synthetase and Organization, Localization, and Differential Splicing of Its Gene J. Biol. Chem., May 31, 1996; 271(22): 13077 - 13087. [Abstract] [Full Text] [PDF]

				K. Roy, K. Mitsugi, S. Sirlin, B. Shane, and F. M. Sirotnak Different Antifolate-resistant L1210 Cell Variants with either Increased or Decreased Folylpolyglutamate Synthetase Gene Expression at the Level of mRNA Transcription J. Biol. Chem., November 10, 1995; 270(45): 26918 - 26922. [Abstract] [Full Text] [PDF]