Malewski T, Zwierzchowski L
Institute of Genetics and Animal Breeding, Polish Academy of Sciences.
Tsitol Genet. 1997 Jul-Aug;31(4):58-69.
In the mammary gland four tissue-specific transcription factors have been found involved in the regulation of milk protein genes: mammary gland-specific nuclear factor (MGF), milk protein binding factor (MPBF), pregnancy-specific mammary nuclear factor (PMF), mammary cell-activating factor (MAF). Rabbit beta-casein gene promoter contains motifs highly homologous (89-100%) to MGF, MAF and PMF consensus sequences. These transcription factors were analysed simultaneously using electrophoretic mobility shift assays (EMSA) on nuclear protein extracts derived from pregnant or lactating rabbit mammary glands. The specificity of these complexes was analysed in cross-competition EMSA experiments. It was shown that in the rabbit mammary gland the DNA-binding activities of MGF, MAF and PMF change during pregnancy and lactation. Protein extracts of nuclei isolated from mammary glands of 15-day pregnant rabbits form fast-migrating low-specific complexes with MGF, MAF and PMF oligonucleotide probes; in the extracts from mammary glands of late pregnant (day 25) and lactating (day 5) rabbits additional slowly-migrating highly specific DNA-protein complexes are formed. Their appearance changes in parallel with the activation of beta-casein gene expression as measured by run-on gene transcription and beta-casein mRNA accumulation.
在乳腺中，已发现四种组织特异性转录因子参与乳蛋白基因的调控：乳腺特异性核因子（MGF）、乳蛋白结合因子（MPBF）、妊娠特异性乳腺核因子（PMF）、乳腺细胞激活因子（MAF）。兔β-酪蛋白基因启动子含有与MGF、MAF和PMF共有序列高度同源（89 - 100%）的基序。使用电泳迁移率变动分析（EMSA）对来自妊娠或泌乳兔乳腺的核蛋白提取物同时分析这些转录因子。在交叉竞争EMSA实验中分析这些复合物的特异性。结果表明，在兔乳腺中，MGF、MAF和PMF的DNA结合活性在妊娠和泌乳期间发生变化。从妊娠15天的兔乳腺分离的细胞核蛋白提取物与MGF、MAF和PMF寡核苷酸探针形成快速迁移的低特异性复合物；在妊娠后期（第25天）和泌乳期（第5天）兔乳腺的提取物中，形成了额外的缓慢迁移的高特异性DNA - 蛋白质复合物。它们的出现与通过连续基因转录和β-酪蛋白mRNA积累所测量的β-酪蛋白基因表达的激活平行变化。
