The Arabidopsis STV1 protein, responsible for translation reinitiation, is required for auxin-mediated gynoecium patterning
PLANT CELL
Authors: Nishimura, T; Wada, T; Yamamoto, KT; Okada, K
Abstract
Ribosomal protein L24 (RPL24) is implicated in translation reinitiation of polycistronic genes. A newly isolated Arabidopsis thaliana short valve1 (stv1) mutant, in which one of the RPL24-encoding genes, RPL24B, is deleted, shows specific defects in the apical-basal patterning of the gynoecium, in addition to phenotypes induced by ribosome deficiency. A similar gynoecium phenotype is caused by mutations in the auxin response factor (ARF) genes ETTIN (ETT) and MONOPTEROS (MP), which have upstream open reading frames (uORFs) in their 5'-transcript leader sequences. Gynoecia of a double mutant of stv1 and a weak ett mutant allele are similar to those of a strong ett allele, and transformation with a uORF-eliminated ETT construct partially suppressed the stv1 gynoecium phenotype, implying that STV1 could influence ETT translation through its uORFs. Analyses of 5'-leader-reporter gene fusions showed that the uORFs of ETT and MP negatively regulate the translation of the downstream major ORFs, indicating that translation reinitiation is an important step for the expression of these proteins. Taken together, we propose that perturbation of translation reinitiation of the ARF transcripts causes the defects in gynoecium patterning observed in the stv1 mutant.
The p53 Tumor Suppressor Causes Congenital Malformations in Rpl24-Deficient Mice and Promotes Their Survival
MOLECULAR AND CELLULAR BIOLOGY
Authors: Barkic, Martina; Crnomarkovic, Sladana; Grabusic, Kristina; Bogetic, Ivana; Panic, Linda; Tamarut, Sanda; Cokaric, Maja; Jeric, Ines; Vidak, Sandra; Volarevic, Sinisa
Abstract
Hypomorphic mutation in one allele of ribosomal protein l24 gene (Rpl24) is responsible for the Belly Spot and Tail (Bst) mouse, which suffers from defects of the eye, skeleton, and coat pigmentation. It has been hypothesized that these pathological manifestations result exclusively from faulty protein synthesis. We demonstrate here that upregulation of the p53 tumor suppressor during the restricted period of embryonic development significantly contributes to the Bst phenotype. However, in the absence of p53 a large majority of Rpl24(Bst/+) embryos die. We showed that p53 promotes survival of these mice via p21-dependent mechanism. Our results imply that activation of a p53-dependent checkpoint mechanism in response to various ribosomal protein deficiencies might also play a role in the pathogenesis of congenital malformations in humans.