Shen, Ying H.Godlewski, JakubBronisz, AgnieszkaZhu, JunComb, Michael J.Avruch, JosephTzivion, Guri2019-10-052003Shen, Ying H., Jakub Godlewski, Agnieszka Bronisz, Jun Zhu, Michael J. Comb, Joseph Avruch, and Guri Tzivion. 2003. “Significance of 14-3-3 Self-Dimerization for Phosphorylation-Dependent Target Binding.” Molecular Biology of the Cell 14 (11): 4721–33. https://doi.org/10.1091/mbc.e02-12-0821.1059-15241939-4586http://nrs.harvard.edu/urn-3:HUL.InstRepos:4148294414-3-3 proteins via binding serine/threonine-phosphorylated proteins regulate diverse intracellular processes in all eukaryotic organisms. Here, we examine the role of 14-3-3 self-dimerization in target binding, and in the susceptibility of 14-3-3 to undergo phosphorylation. Using a phospho-specific antibody developed against a degenerated mode-1 14-3-3 binding motif (RSxpSxP), we demonstrate that most of the 14-3-3-associated proteins in COS-7 cells are phosphorylated on sites that react with this antibody. The binding of these phosphoproteins depends on 14-3-3 dimerization, inasmuch as proteins associated in vivo with a monomeric 14-3-3 form are not recognized by the phospho-specific antibody. The role of 14-3-3 dimerization in the phosphorylation-dependent target binding is further exemplified with two well-defined 14-3-3 targets, Raf and DAF-16. Raf and DAF-16 can bind both monomeric and dimeric 14-3-3; however, whereas phosphorylation of specific Raf and DAF-16 sites is required for binding to dimeric 14-3-3, binding to monomeric 14-3-3 forms is entirely independent of Raf and DAF-16 phosphorylation. We also find that dimerization diminishes 14-3-3 susceptibility to phosphorylation. These findings establish a significant role of 14-3-3 dimerization in its ability to bind targets in a phosphorylation-dependent manner and point to a mechanism in which 14-3-3 phosphorylation and dimerization counterregulate each other.en-USJournal Article2019-10-0510.1091/mbc.E02-12-0821