MOLELCULAR BIOLOGY OF PHOTOTRANSDUCTION

我们鉴定了人和小鼠的S抗原基因，33K 小鼠和人类的蛋白质基因。S的抗原基因是 全长约50kbp，包含16个外显子和15个内含子， 由97%的内含子和3%的外显子组成。5~-侧翼区域 其中约1.5kbp的基因没有已知的调控元件 用于转录，如TATA、GC或CCAAT盒。 控制组织限制性的调控序列和核因子 对小鼠arrestin基因的表达进行了研究。结果是 结果表明，虽然近端启动子序列-38到+304足以 直接低水平的视网膜特异性基因表达，序列延伸 上游-209支持视网膜中更高水平的表达 以及在晶状体、松果体和大脑中可检测到的表达。机智 N 位置-205和-185之间的间隔是包含两个 六角体的直接重复，TGACCT。近端的启动子结合了三个 明显的视网膜特异性核因子，BP1，BP2和BP3，通过 以-25和-15位置为中心的重叠序列。BP1和 BP3还识别在启动子区域中发现的密切相关的序列 其他几种脊椎动物的光感受器特异基因。此外， BP1的共识结合位点命名为PCE1，与RCS1相同，并且 已知在诱导光感受器特异性G E 在果蝇中的表达。结果表明，PCE1和 RCS1在功能和结构上都很相似，尽管 苍蝇和脊椎动物视觉系统的显著差异， 参与光感受器特异性基因表达的转录机制 在进化上是非常保守的。

We have characterized the S-antigen genes from human and mouse, 33K protein genes from mouse and human. The S-antigen genes were approximately 50 kbp in length, contained 16 exons and 15 introns, and were composed of 97 percent intron and 3 percent exon. The 5~-flanking regions of the genes, approximately 1.5 kbp long, had no known regulatory elements for transcription such as TATA, GC, or CCAAT boxes. Regulatory sequences and nuclear factors governing tissue-restricted expression of the mouse arrestin gene were investigated. The results showed that while proximal promoter sequence -38 to +304 are sufficient to direct low levels of retina-specific gene expression, sequences extending upstream to position -209 support higher levels of expression in the retina as well as detectable expression in the lens, pineal gland, and brain. Wit n the interval between positions -205 and -185 is a region that contains two direct repeats of the hexamer, TGACCT. The proximal promoter binds three apparently retina-specific nuclear factors, Bp1, Bp2, and Bp3, through overlapping sequences centered between positions -25 and -15. Bp1 and Bp3 also recognize a closely related sequence found in the promoter regions of several other vertebrate photoreceptor-specific genes. Moreover, the consensus binding site for Bp1, designated PCE1, is identical to RCS1, an element known to play a critical role in eliciting photoreceptor-specific g e expression in Drosophila melanogaster. The results suggest that PCE1 and RCS1 are functionally, as well as structurally, similar and, that despite marked differences in the fly and vertebrate visual system, the transcriptional machinery involved in photoreceptor-specific gene expressio has been strongly evolutionarily conserved.