Identification and expression pattern of a second isoform of the newt alpha retinoic acid receptor.
Identification and expression pattern of a second isoform of the newt alpha retinoic acid receptor.
复制标题
蝾螈α视黄酸受体第二种亚型的鉴定和表达模式。
作者：
Clifton W. Ragsdale;P. B. Gates;J. Brockes
维甲酸能够通过重新指定再生胚泡的位置记忆来改变再生两栖动物肢体的模式(1)。核受体类转录因子对全反式维甲酸的反应被认为是介导这些效应的有利因素。维甲酸受体(RAR)在脊椎动物中已被鉴定为三种亚型--RAR7及其尾目近亲RAR6、RAR/3和RARA，每种亚型都以N端序列(1-3)的不同亚型存在。这种多样性表明，研究再生中位置再指定的机制的首要任务是清点驻留在胚泡中的RARs，并评估它们的相对水平。最丰富的胚芽RAR是6受体，它以多种亚型存在(4)。在胚泡中也很容易检测到RARA信息，但到目前为止，只克隆了一种两栖动物亚型a，[5]。在此，我们报道了从XZAP的Newt Tail文库中分离到第二个RAR基因的异构体。其完整的核苷酸序列可在EMBL登录号Z14254下获得。N-末端区域A的序列比较(图1)将这个RAR与X2RAR类似物联系在一起，与小鼠A2受体有54%的同源性。这个值接近Newt 62和小鼠y2受体之间发现的58%的同源性(4)。相比之下，xi受体的可比值似乎范围更广；Newt a，区域A与小鼠？I的相同程度为76%，而Newt 51受体的N-末端与小鼠的y？受体在重叠区域的相同程度不到45%。
Retinoic acid is able to alter pattern in regenerating amphibian limbs by respecifying the positional memory of the regeneration blastema (1). Transcription factors of the nuclear receptor class that are responsive to all-?ra/w-retinoic acid are favored to mediate these effects. Three subtypes of retinoic acid receptor (RAR) have been identified in vertebrates — RAR7 and its urodele relative RAR6, RAR/3 and RARa, each occurring in multiple isoforms distinguished by their N-terminal sequences (1-3). This diversity suggests that a first task in the study of the mechanisms of positional respecification in regeneration is an inventory of RARs resident in the blastema and an assessment of their relative levels. The most abundant blastemal RAR is the 6 receptor, which is present in multiple isoforms (4). RARa message is also readily detected in the blastema, but to date only one amphibian isoform, a,, has been cloned (5). We report here the isolation of a RAR cDNA for a second a isoform from a newt tail library prepared in XZAP. Its complete nucleotide sequence is available under EMBL accession number Z14254. Sequence comparisons for the N-terminal region A (Figure 1) affiliate this RAR with the X2RAR paralogs, presenting 54% identity with the mouse a2 receptor. This value is close to the 58% identity found between the newt 62 and mouse y2 receptors (4). The comparative values for the xi receptors, by contrast, appear to range more widely; the newt a, region A is 76% identical with that of mouse «i whereas the newt 51 receptor N-terminal is less than 45% identical with that of the mouse y{ receptor over their region of overlap (5).