Cho Young-Hee, Yoo Sang-Dong, Sheen Jen
Department of Molecular Biology, Massachusetts General Hospital, Department of Genetics, Harvard Medical School, Boston, MA 02114, USA.
Cell. 2006 Nov 3;127(3):579-89. doi: 10.1016/j.cell.2006.09.028.
Arabidopsis hexokinase1 (HXK1) is a glucose sensor that integrates nutrient and hormone signals to govern gene expression and plant growth in response to environmental cues. How the metabolic enzyme mediates glucose signaling remains a mystery. By coupling proteomic and binary-interaction screens, we discover two nuclear-specific HXK1 unconventional partners: the vacuolar H(+)-ATPase B1 (VHA-B1) and the 19S regulatory particle of proteasome subunit (RPT5B). Remarkably, vha-B1 and rpt5b mutants uniquely share a broad spectrum of glucose response defects with the HXK1 mutant gin2 (glucose-insensitive2). Genetic and chromatin immunoprecipitation analyses suggest that the nuclear HXK1 forms a glucose signaling complex core with VHA-B1 and RPT5B that directly modulates specific target gene transcription independent of glucose metabolism. The findings support a model in which conserved metabolic enzymes and proteins of well-established activities may perform previously unrecognized nuclear functions.
拟南芥己糖激酶1（HXK1）是一种葡萄糖传感器，它整合营养和激素信号，以响应环境线索来调控基因表达和植物生长。这种代谢酶如何介导葡萄糖信号传导仍是一个谜。通过结合蛋白质组学和二元相互作用筛选，我们发现了两个核特异性的HXK1非常规伴侣：液泡H⁺-ATP酶B1（VHA-B1）和蛋白酶体亚基19S调节颗粒（RPT5B）。值得注意的是，vha-B1和rpt5b突变体与HXK1突变体gin2（葡萄糖不敏感2）独特地共享了广泛的葡萄糖反应缺陷。遗传和染色质免疫沉淀分析表明，核HXK1与VHA-B1和RPT5B形成了一个葡萄糖信号复合物核心，该核心直接调节特定靶基因的转录，而与葡萄糖代谢无关。这些发现支持了一个模型，即保守的代谢酶和具有既定活性的蛋白质可能执行以前未被认识的核功能。
