RESUMEN
HDR syndrome is an autosomal dominant disorder characterized by hypoparathyroidism, sensorineural deafness, and renal anomaly caused by mutation of the GATA3 gene located at chromosome 10p15. We report the case of a neonate with HDR syndrome and a novel GATA3 mutation. We performed genetic and functional analysis of GATA3 in this patient and identified a novel heterozygous 1516G> C missense mutation in exon 5, resulting in a cysteine-to-serine substitution at codon 321 (Cys321Ser). Mutated and wild-type GATA3 proteins were expressed at a similar level in vitro, indicating that the mutated GATA3 protein was stable. Luciferase assay revealed that the Cys321Ser-mutated GATA3 lacked transactivation activity due to loss of DNA-binding activity as confirmed by gel shift assay. Moreover, mutated GATA3 exerted a dominant-negative effect over the transactivation activity of wild-type GATA3. These findings indicate that not only haploinsufficiency of GATA3 but also the dominant-negative effect of Cys321Ser-mutated GATA3 might have been responsible for the HDR syndrome phenotype of our patient.
Asunto(s)
Factor de Transcripción GATA3/genética , Genes Dominantes , Proteínas Mutantes , Animales , Secuencia de Bases , Células COS , Técnicas de Cultivo de Célula , Chlorocebus aethiops , Proteínas de Unión al ADN/metabolismo , Factor de Transcripción GATA3/metabolismo , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Células HEK293 , Pérdida Auditiva Sensorineural/genética , Humanos , Hipoparatiroidismo/genética , Recién Nacido , Masculino , Datos de Secuencia Molecular , Proteínas Mutantes/genética , Mutación Missense/genética , Nefrosis/genética , Activación TranscripcionalRESUMEN
The movement protein (MP) of Tomato mosaic virus (ToMV) was reported previously by us to be phosphorylated in vitro by a cellular protein kinase(s) that exhibited several characteristics of casein kinase 2 (CK2). To characterize further this CK2-like cellular kinase, we have cloned cDNAs encoding the CK2 catalytic subunit from tobacco and compared the properties of the recombinant protein with those of the CK2-like cellular kinase. The recombinant CK2 catalytic subunit formed a complex with ToMV MP and phosphorylated it, similar to the CK2-like cellular kinase. Phosphoamino acid analyses of various mutant MPs altered near the C terminus revealed that the recombinant CK2 catalytic subunit phosphorylated serine-261, while the CK2-like cellular kinase phosphorylated both serine-261 and threonine-256. Both kinases were suggested to phosphorylate an additional serine residue(s) in regions other than the C-terminal peptide. The results are consistent with our previous prediction of involvement of CK2 in phosphorylation of ToMV MP.