Philips Alana S, Kwok Juliana C, Chong Beng H
Centre for Vascular Research, Department of Medicine, St. George Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia.
J Biol Chem. 2007 Aug 24;282(34):24915-27. doi: 10.1074/jbc.M701789200. Epub 2007 Jun 4.
Nucleocytoplasmic transport of GATA-4 is important in maintaining and regulating normal cardiogenesis and heart function. This report investigates the detailed mechanisms of GATA-4 nuclear transport. We characterized a nonclassical nuclear localization signal between amino acids 270 and 324 that actively transports GATA-4 into the nucleus of both HeLa cells and cardiac myocytes. Fine mapping studies revealed four crucial arginine residues within this region that mediate active transport predominantly through the nonclassical pathway via interaction with importin beta. These four residues were also essential for the DNA binding activity of GATA-4 and transcriptional activation of cardiac-specific genes. Interestingly, mutation of these residues not only inhibited DNA binding and gene transcription but also resulted in a preferential accumulation of the GATA-4 protein in distinct subnuclear speckles. A cardiac myocyte-specific, chromosome maintenance region 1-dependent nuclear export signal consisting of three essential leucine residues was also identified. The current study provides detailed information on the nuclear shuttling pathways of GATA-4 that represents an additional mechanism of gene regulation.
GATA-4的核质转运对于维持和调节正常心脏发育及心脏功能至关重要。本报告研究了GATA-4核转运的详细机制。我们鉴定了一个位于氨基酸270至324之间的非经典核定位信号，该信号可将GATA-4主动转运至HeLa细胞和心肌细胞的细胞核中。精细定位研究揭示了该区域内四个关键的精氨酸残基，它们主要通过与输入蛋白β相互作用，经非经典途径介导主动转运。这四个残基对于GATA-4的DNA结合活性及心脏特异性基因的转录激活也至关重要。有趣的是，这些残基的突变不仅抑制了DNA结合和基因转录，还导致GATA-4蛋白在不同的核内斑点中优先积累。还鉴定了一个由三个必需亮氨酸残基组成的心肌细胞特异性、依赖染色体维持区域1的核输出信号。当前研究提供了关于GATA-4核穿梭途径的详细信息，这代表了一种额外的基因调控机制。
