Kornfeld K, Saint R B, Beachy P A, Harte P J, Peattie D A, Hogness D S
Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305.
Genes Dev. 1989 Feb;3(2):243-58. doi: 10.1101/gad.3.2.243.
The 77-kb primary transcript of the homeotic Ultrabithorax (Ubx) gene is alternatively spliced to yield at least five different coding regions. Each is restricted to either a 3.2- or a 4.3-kb size class generated by alternative polyadenylation. The pathways for splicing and polyadenylation are therefore coordinately regulated, and because the relative abundance of the respective mRNAs varies throughout development, these pathways also appear to be developmentally regulated. Translation of these mRNAs yields a family of Ubx proteins characterized by constant amino- and carboxy-proximal regions of 247 and 99 amino acid residues, respectively. Members of this family are distinguished by a short variable region that links the constant regions and consists of different combinations of three optional elements of 9, 17, and 17 residues. Only four amino acid residues separate this variable region from the 60-residue homeo domain of the carboxy-terminal constant region. This proximity suggests that functional differences among the Ubx proteins derive from the differential effects of their variable regions on the DNA-binding capacity of the homeo domain. An argument is made that these functional differences are tissue specific.
同源异型基因超双胸节（Ubx）的77kb初级转录本经过可变剪接，产生至少五个不同的编码区。每个编码区都局限于由可变聚腺苷酸化产生的3.2kb或4.3kb大小类别。因此，剪接和聚腺苷酸化途径受到协同调节，并且由于各个mRNA的相对丰度在整个发育过程中有所不同，这些途径似乎也受到发育调控。这些mRNA的翻译产生了一个Ubx蛋白家族，其特征分别是在氨基末端和羧基末端有247个和99个氨基酸残基的恒定区域。该家族成员的区别在于连接恒定区域的一个短可变区域，该可变区域由9、17和17个残基的三个可选元件的不同组合组成。这个可变区域与羧基末端恒定区域的60个残基的同源结构域仅相隔四个氨基酸残基。这种接近性表明，Ubx蛋白之间的功能差异源于其可变区域对同源结构域DNA结合能力的不同影响。有一种观点认为，这些功能差异是组织特异性的。
