Functional Characterization of LIMK2 carrying LIM and PDZ Domains in the Developmental and Tumorigenic Process.

我们之前分离了人类 LIMK2 基因，并鉴定了两个替代转录物 LIMK2a 和 LIMK2b，它们以组织特异性方式进行差异调节。为了详细检查这种差异组织特异性表达，进行了 RNase 保护测定，该测定证明了 LIMK2 同工型的三种表达模式。在消化器官中，LIMK2a转录本优先在胎儿和成人组织中表达；在脑和肺中，LIMK2a转录本主要仅在胎儿组织中表达，而在胎盘中，LIMK2b转录本的表达量比LJMK2a更丰富。为了进一步研究这一机制和所涉及的转录因子，我们从噬菌体基因组文库中分离了两个不同的5'上游区域，发现LIMK2a和2b启动子都具有单一的主要转录起始位点和无TATA启动子的特征。转录活性的荧光素酶报告基因分析揭示了两个启动子内的正调控区和负调控区。 RORα1可能参与LIMK2b表达的正向调节，而MZF-1可能以不同的方式调节LIMK2a和2b。 LIMK2 基因的基因组结构也被确定。这些发现应该有助于更好地理解 LIMK 家族可能具有的多种功能

We previously isolated the human LIMK2 gene and identified two alternative transcripts, LIMK2a and LIMK2b, which were differentially regulated in a tissue-specific manner. To examine this differential tissue-specific expression in detail, an RNase protection assay was performed, which demonstrated three expression patterns of the LIMK2 isoforms. In digestive organs, the LIMK2a transcripts were preferentially expressed in fetal and adult tissues ; in brain and lung, the LIMK2a transcript was predominantly expressed only in fetal tissue, and in placenta, the LIMK2b transcript was expressed more abundantly than that of LJMK2a. To further investigate this mechanism and the transcription factors involved, we isolated the two distinct 5' upstream regions from the phage genomic library, and found that both LIMK2a and 2b promoters have a single major transcription initiation site and thecharacteristics of a TATA-less promoter. A luciferase reporter assay of the transcriptional activity revealed positive as well as negative regulatory regions within both promoters. The RORalphal may be involved in the positive regulation for the LIMK2b expression, while the MZF-1 might regulate both LIMK2a and 2b in a different manner. The genomic structure of the LIMK2 gene was also determined. These findings should lead to a better understanding of the possibly diverse functions of the LIMK family