Regulatory mechanisms for the MHC class III genes

小鼠C4和性别限制蛋白（Slp）是由小鼠主要组织相容性复合体III的两个最近重复的基因编码的。这些基因在小鼠品系中的许多表达变异的可用性使它们成为研究真核基因在发育、激素和组织特异性控制下的调控的有吸引力的系统。我们从几个小鼠品系中分离并鉴定了这些基因的cDNA和基因组DNA克隆，这些基因在C4和slp的表达上表现出有趣的变化。我们通过各种分子遗传技术得到的实验结果可以总结如下：1。携带H-2^k单倍型的小鼠品系具有低C4产生率的特点。利用高产C4小鼠（B10）和低产C4小鼠（B10）的肝细胞，用Northern印迹法测定C4 mRNA，用核电泳法测定核C4 RNA。此外，我们还检测了这些菌株C4基因的5'侧区对转染细胞的反式调控活性。结果清楚地表明，低C4合成主要控制在转录后和翻译前水平。为了阐明C4基因（宪法）和Slp基因（睾酮诱导）表达方式差异的分子基础，我们比较了从FM菌株分离的这两个基因的核苷酸序列。此外，我们在转染的细胞中使用CAT检测了5'侧翼区片段的转录调节活性。我们确定了这些基因区域的功能域，这些功能域似乎可以解释C4和Slp基因的基因表达差异。我们从C3H的cosmid文库中分离并鉴定了所有c4相关基因。W7菌株显示出一种特殊的Slp（宪制表达）表达模式。我们发现三个明显的Slp基因确实由c4衍生的5‘半和Slp衍生的3’半组成。通过与C4和Slp基因的核苷酸序列比较，我们得出结论，这些重组基因是由基因中心部分的多次交叉衍生而来。少

Mouse C4 and Sex-limited protein(Slp) are encoded by two recently duplicated genes of the major histocompatibility complex III of the mouse. The availability of many expression variants for these genes among mouse strains makes them the attractive system in which the regulation of eukaryotic genes under developmental, hormonal and tissue specific control can be studied. We isolated and characterized cDNA and genomic DNA clones for these genes from several mouse strains which show interesting variation for the expression of C4 and slp. Our experimental results obtained by various molecular genetic techniques can be summarized as follows.1. The mouse strains carrying H-2^k haplotype are characterized as low C4 producers. We measured C4 mRNA by Northern blotting and nuclear C4 RNA by nuclear run on assay using the hepatocytes from high C4 producing mouse(B10) and low C4 producing mouse(B10.BR). Furthermore we tested the 5'flanking regions of the C4 genes from these strains for their trans … More criptional regulatory activity with transfected cells. The results clearly showed that the low C4 bisynthesis is mainly controlled at the posttranscriptional and pretranslational level.2. To elucidate the molecular basis underlying the difference in the mode of expression of C4 gene(constitutional) and Slp gene(testosterone induced), we compared the nucleotide sequences of these two genes isolated from FM strain. Furthermore we tested the 5'flanking region fragments for transcriptional regulatory cativity using CAT assay in transfected cells. We identified the functional domains in the regions of these genes that appear to explain the difference in the gene expression of the C4 and Slp genes.3. We isolated and characterized all of C4-related genes from the cosmid library of C3H.W7 strain that shows an extraordinary mode of expression of Slp(constitutional expression). We found the three of apparent Slp genes indeed consisting of the C4-derived 5' half and Slp-derived 3' half. By comparing their nucleotide seguences with those of C4 and Slp genes, we concluded that these recombinant genes are derived by multiple cross over in the central portions of the gene. Less