Mihailović Mirjana, Dinić Svetlana, Bogojević Desanka, Ivanović-Matić Svetlana, Uskoković Aleksandra, Arambasić Jelena, Grigorov Ilijana, Grdović Nevena, Vidaković Melita, Martinović Vesna, Petrović Miodrag, Poznanović Goran
Department of Molecular Biology, Institute for Biological Research, Belgrade, Serbia.
Acta Biochim Pol. 2007;54(2):331-40. Epub 2007 Jun 12.
Expression of the rat alpha(2)-macroglobulin (MG) gene undergoes dynamic changes throughout an individual's life and during the acute-phase (AP) response. Details of the participation of the STAT family of transcription factors in its control remain incompletely understood. Here we examined the involvement of STAT5b in MG gene expression during development and the AP response. Immuno-blot analysis revealed the highest nuclear level of STAT5b in the fetus and during postnatal development, whereas in the adult it decreased. Stimulation of MG expression during the AP response was accompanied by a decrease in STAT5b. Examination of STAT5b localization revealed that the relative concentrations of STAT5b were higher in the nuclear matrix than in the nuclear extract. Affinity chromatography with the extended promoter region of the MG gene (-825/+12), followed by immuno-blot analysis, revealed dynamic changes in STAT5b binding. The highest concentration of the promoter-binding form of STAT5b was observed in the fetus. As postnatal development progressed, the level of promoter-bound STAT5b decreased and in the adult liver it was the lowest. Stimulation of MG gene expression during the AP response in both the fetus and adult was accompanied by significantly decreased STAT5b binding to the MG promoter. The AP response was accompanied by lower levels of STAT5b serine and tyrosine phosphorylation in both fetus and adult. In the nuclear matrix derived from adult tissues, tyrosine phosphorylated species were completely absent. We conclude that developmental-stage differences in the mechanisms that determine STAT5b nuclear localization contribute to its activity in vivo.
大鼠α(2)-巨球蛋白（MG）基因的表达在个体的一生中以及急性期（AP）反应期间会发生动态变化。转录因子STAT家族在其调控中的参与细节仍未完全了解。在此，我们研究了STAT5b在发育过程和AP反应期间对MG基因表达的影响。免疫印迹分析显示，STAT5b在胎儿期和出生后发育阶段的细胞核水平最高，而在成年期则下降。AP反应期间MG表达的刺激伴随着STAT5b的减少。对STAT5b定位的检查显示，STAT5b在核基质中的相对浓度高于核提取物中的浓度。用MG基因的延伸启动子区域（-825/+12）进行亲和层析，随后进行免疫印迹分析，揭示了STAT5b结合的动态变化。在胎儿中观察到STAT5b启动子结合形式的浓度最高。随着出生后发育的进行，启动子结合的STAT5b水平下降，在成年肝脏中最低。胎儿和成年个体在AP反应期间MG基因表达的刺激都伴随着STAT5b与MG启动子结合的显著减少。AP反应伴随着胎儿和成年个体中STAT5b丝氨酸和酪氨酸磷酸化水平的降低。在成年组织来源的核基质中，完全不存在酪氨酸磷酸化的物种。我们得出结论，决定STAT5b核定位的机制在发育阶段的差异有助于其在体内的活性。
