Vladychenskaya Irina P, Dergunova Lyudmila V, Dmitrieva Veronica G, Limborska Svetlana A
Department of Human Molecular Genetics, Institute of Molecular Genetics RAS, Kurchatov sq., 2, 123182 Moscow, Russia.
Gene. 2004 Sep 1;338(2):257-65. doi: 10.1016/j.gene.2004.06.003.
Prior investigation of human brain cDNA libraries revealed an evolutionarily conserved gene MOB that has been cloned in silico on chromosome 10. To elucidate its biological role, we performed structural and functional analysis of its transcripts. Applying an expressed sequence tag (EST) approach, we specified the sequence of the predicted MOB transcript and found another four exons to belong to the 5'- end of the MOB gene; the newly constructed MOB transcript was detected in vitro. Here, we report MOB to comprise at least 11 exons and 10 introns and to span more than 320 kb of the genomic sequence. We propose complex regulation of MOB gene activity at a transcriptional level, based on its expression pattern. Thus, in the human cerebellum, we discovered multiple alternatively spliced products of MOB differing in their coding portion; one of the alternative transcripts was demonstrated to lack the longest coding exon VII. MOB was expressed at very low levels in a wide spectrum of human tissues: most abundantly in the brain and in the kidney. Two transcription initiation sites were found for MOB and two alternative promoters were suggested to govern its expression. We believe that MOB activity is also regulated at the posttranscriptional level. In the constructed MOB transcript, the extended multiexon 5'-untranslated region (UTR) together with the weak context of the translation start ATG codon are considered as potent translator inhibitors. Modulation of MOB translation efficiency is proposed based on the appropriate alternative splicing events within the 5'-UTR. The MOB 3'-UTR is anticipated to mediate message instability. We thus suggest that this MOB transcript may be a labile short-lived molecule with strong regulation of its translational efficiency. We believe that MOB gene activity is controlled at least at the transcriptional and the posttranscriptional levels, strictly regulating the amount of the encoded protein product.
先前对人类大脑cDNA文库的研究揭示了一个进化上保守的基因MOB，该基因已通过电子克隆定位在10号染色体上。为了阐明其生物学作用，我们对其转录本进行了结构和功能分析。应用表达序列标签（EST）方法，我们确定了预测的MOB转录本的序列，并发现另外四个外显子属于MOB基因的5'端；新构建的MOB转录本在体外被检测到。在此，我们报告MOB至少由11个外显子和10个内含子组成，跨越超过320 kb的基因组序列。基于其表达模式，我们提出MOB基因活性在转录水平受到复杂调控。因此，在人类小脑中，我们发现了MOB的多种可变剪接产物，它们的编码部分不同；其中一种可变转录本被证明缺少最长的编码外显子VII。MOB在广泛的人类组织中表达水平非常低：在大脑和肾脏中表达最为丰富。发现了MOB的两个转录起始位点，并提出两个可变启动子调控其表达。我们认为MOB活性在转录后水平也受到调控。在构建的MOB转录本中，延伸的多外显子5'非翻译区（UTR）以及翻译起始ATG密码子的弱上下文被认为是有效的翻译抑制剂。基于5'-UTR内适当的可变剪接事件，提出了对MOB翻译效率的调节。预计MOB的3'-UTR介导信息不稳定性。因此，我们认为这种MOB转录本可能是一种不稳定的短寿命分子，其翻译效率受到严格调控。我们相信MOB基因活性至少在转录和转录后水平受到控制，严格调节编码蛋白产物的量。
