Julia Mergner and Claus Schwechheimer are very happy to have contributed to the ALF4 study of the Estelle lab from UC San Diego.
The Arabidopsis ALF4 protein is a regulator of SCF E3 ligases.
Rammyani Bagchi, Charles W Melnyk, Gideon Christ, Martin Winkler, Kerstin Kirchsteiner, Mohammad Salehin, Julia Mergner, Michael Niemeyer, Claus Schwechheimer, Luz Irina A Calderón Villalobos, Mark Estelle
The cullin-RING E3 ligases (CRLs) regulate diverse cellular processes in all eukaryotes. CRL activity is controlled by several proteins or protein complexes, including NEDD8, CAND1, and the CSN. Recently, a mammalian protein called Glomulin (GLMN) was shown to inhibit CRLs by binding to the RING BOX (RBX1) subunit and preventing binding to the ubiquitin-conjugating enzyme. Here, we show that Arabidopsis ABERRANT LATERAL ROOT FORMATION4 (ALF4) is an ortholog of GLMN. The alf4 mutant exhibits a phenotype that suggests defects in plant hormone response. We show that ALF4 binds to RBX1 and inhibits the activity of SCFTIR1, an E3 ligase responsible for degradation of the Aux/IAA transcriptional repressors. In vivo, the alf4 mutation destabilizes the CUL1 subunit of the SCF. Reduced CUL1 levels are associated with increased levels of the Aux/IAA proteins as well as the DELLA repressors, substrate of SCFSLY1. We propose that the alf4 phenotype is partly due to increased levels of the Aux/IAA and DELLA proteins.
