Miwa Arisa, Higuchi Takashi, Kobayashi Shunsuke
Department of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555, Japan.
Biochim Biophys Acta. 2006 Nov;1760(11):1675-81. doi: 10.1016/j.bbagen.2006.08.027. Epub 2006 Sep 14.
Tissue-specific translational regulation is important for gene expression. YB-1 binds to mRNAs to form mRNPs and affects translation. In this study we investigated expression and polysome association of YB-1 in various tissues at different stages in the lifespan of mice. YB-1 levels decreased markedly with growth in brain, heart and muscle, but increased in the spleen. In lung, kidney and testis, the levels of YB-1 diminished with aging. In liver, no significant change in the level of YB-1 was observed throughout life. We further showed that the distribution pattern of YB-1 on a sucrose gradient differed according to tissue. Moreover, the distribution pattern of YB-1 changed drastically with growth in the liver. In 5-day-old liver, YB-1 was distributed almost exclusively in nonpolysomal fractions, whereas in 4-week-old liver, it was associated with heavy-sedimenting polysomes, as was the case in 5-day-old brain. Immunohistochemical analysis revealed that YB-1 is mainly a cytoplasmic protein in these tissues. Our results indicate that the expression and polysome association of YB-1 are regulated with growth or aging in a tissue-specific manner, presumably to control gene expression at the translational level in each tissue.
组织特异性翻译调控对基因表达很重要。YB-1与mRNA结合形成mRNA-蛋白质复合物并影响翻译。在本研究中，我们调查了小鼠生命周期中不同阶段YB-1在各种组织中的表达及与多核糖体的结合情况。随着生长，脑、心脏和肌肉中的YB-1水平显著下降，但脾脏中的YB-1水平升高。在肺、肾和睾丸中，YB-1水平随衰老而降低。在肝脏中，整个生命周期内YB-1水平未观察到显著变化。我们进一步表明，YB-1在蔗糖梯度上的分布模式因组织而异。此外，肝脏中YB-1的分布模式随生长而发生剧烈变化。在5日龄的肝脏中，YB-1几乎只分布在非多核糖体组分中，而在4周龄的肝脏中，它与重沉降多核糖体相关，5日龄的脑也是如此。免疫组织化学分析显示，在这些组织中YB-1主要是一种细胞质蛋白。我们的结果表明，YB-1的表达及与多核糖体的结合以组织特异性方式随生长或衰老而受到调控，推测是为了在每个组织的翻译水平上控制基因表达。
