Phosphorylation of HDGF S103 regulates its ability to stimulate cell proliferation. A. HDGF-GFP, HDGF-GFP-S103A or HDGF-GFP-S103D fusion proteins were expressed in HEK-293 cells for 24 hours and the cell cycle analyzed in GFP and non-GFP expressing cells by FACS. (n = 4-5, with three replicates for each experiment.) B. Cell cycle analysis of cells expressing the HDGF fusions (GFP) vs non-GFP positive cells from the same experiments in A. # = HDGF vs GFP, * = HDGF-S103A or D vs HDGF. * and # = P ≤ 0.05.