Jump D B, Veit A, Santiago V, Lepar G, Herberholz L
Department of Physiology, Michigan State University, East Lansing 48824.
J Biol Chem. 1988 May 25;263(15):7254-60.
The mRNA coding for the rat liver S14 protein (Mr 17,000, pI 4.9) shows profound increases during postnatal development. In an effort to define the molecular basis for the postnatal rise in mRNAs14 we examined the chromatin organization of the S14 gene, its DNA methylation state, the hepatic expression of mRNAs14, and the in vitro S14 "run-on" activity prior to and after weaning at 21 days postpartum. In animals less than or equal to 15 days of age, the hepatic S14 gene is transcriptionally inactive, mRNAs14 levels are less than or equal to 0.5% of adult levels, and the chromatin organization within 11 kilobases of the 5' end of the S14 gene is similar to that found in tissues not expressing mRNAs14. From 18 to 22 days postpartum, the transcriptional activity of the S14 gene increases greater than or equal to 40-fold and mRNAs14 increases greater than or equal to 100-fold approaching adult levels of expression. Highly specific changes in S14 chromatin structure accompany gene activation. The formation of Hss-1 near the S14 cap site (-65 to -265 base pairs) and Hss-3 -3.3 kilobases upstream from the S14 cap site suggests that changes in DNA-protein interaction at these sites may function in both the tissue-specific and developmental regulation of S14 gene expression. The methylation studies suggest HhaI sites may be a cue for the tissue-specific expression of S14. However, the maintenance of hypermethylated HpaII sites throughout S14 gene activation argues against a role for these sites in either the tissue-specific or developmental regulation of S14 gene expression. These studies show that the principal molecular mechanism accounting for the major rise in mRNAs14 during postnatal development is activation of gene transcription and not stabilization of S14 RNA.
编码大鼠肝脏S14蛋白（分子量17,000，等电点4.9）的信使核糖核酸（mRNA）在出生后的发育过程中显著增加。为了确定出生后mRNA14升高的分子基础，我们研究了S14基因的染色质组织、其DNA甲基化状态、mRNA14的肝脏表达以及产后21天断奶前后的体外S14“连续转录”活性。在小于或等于15日龄的动物中，肝脏S14基因转录无活性，mRNA14水平小于或等于成年水平的0.5%，并且S14基因5'端11千碱基内的染色质组织与在不表达mRNA14的组织中发现的相似。产后18至22天，S14基因的转录活性增加大于或等于40倍，mRNA14增加大于或等于100倍，接近成年表达水平。S14染色质结构的高度特异性变化伴随基因激活。在S14帽位点（-65至-265碱基对）附近形成的Hss-1以及在S14帽位点上游3.3千碱基处形成的Hss-3表明，这些位点处DNA-蛋白质相互作用的变化可能在S14基因表达的组织特异性和发育调控中起作用。甲基化研究表明，HhaI位点可能是S14组织特异性表达的一个线索。然而，在整个S14基因激活过程中，HpaII位点保持高甲基化，这表明这些位点在S14基因表达的组织特异性或发育调控中不起作用。这些研究表明，出生后发育过程中mRNA14主要升高的主要分子机制是基因转录的激活，而不是S14 RNA的稳定。
