FUNCTION OF A TRANSPOSABLE ELEMENT IN YEAST

S.酿酒酵母，Ty sigma， 对tRNA基因具有独特的位置特异性。 Ty Sigma由 由几个kbp的内部序列， sigma重复序列，340 bp序列。 结构研究 在本项目期间进行的，结果是 Ty sigma的发现表明Ty sigma和sigma 几乎只发生在tRNA基因的5'端。 尽管 这种独特的位置特异性，然而，Ty sigma是一种逆转录病毒， 就像转座因子一样，它既有结构上的相似性， 与Ty、copia和脾坏死病毒的序列同源性。 本提案中的研究侧重于三个目标： 1. Ty sigma转录的表征。 几乎是满满的- Ty sigma的长度转录本，其由 费洛蒙，似乎是由交配调节的- 类型已被观察到。 Ty sigma模式 转录后的信息素处理和在不同的 将研究遗传背景。 删除每个 Ty sigma的结束将用于对元素进行排序， 然后创建扫描突变， 参与调节表达并决定 无论它们是积极的还是消极的。 2.识别发生在 tRNA基因和Ty sigma。 Ty sigma插入的效果 在tRNA基因表达之后， SUP 2 tRNATyr基因的表达与 Ty sigma的各种重组构型。 表达 与转录活性相关的Ty sigma， 将确定失活的SUP 2基因。 3. Ty sigma转座测定的开发。 泰西格玛 将被过度表达并转座到基因组中， 转化为质粒携带的tRNA基因靶将被分析。 的 tRNA基因结构序列和tRNA基因 然后，位置特异性中的转录作用可以被 测定 Ty sigma和tRNA基因之间的关联提供了一个独特的 有机会扩大对监管互动的观察 转座因子和附近基因的新基因 和潜在的不同类型的监管。 的位置 Ty sigma的特异性进一步表明，这些研究可以 为我们理解反转录转座子做出了独特的贡献 整合机制。

The sigma compostie element of S. cerevisiae, Ty sigma, is uniquely position specific for tRNA genes. Ty sigma is composed of an internal sequence of several kbp flanked by long terminal repeats of sigma, a 340 bp sequence. The structural studies conducted during the current project, which resulted in the discovery of Ty sigma, showed that both Ty sigma and sigma occur almost exclusively at the 5' ends of tRNA genes. Despite this unique position specificity, however, Ty sigma is a retrovirus- like transposable element which has both structural analogies and sequence homologies with Ty, copia, and spleen necrosis virus. The research in this proposal focuses on three objectives: 1. Characterization of Ty sigma transcription. An almost full- length transcript of Ty sigma, which is regulated by pheromones and which appears to be regulated by mating- type has been observed. The pattern of Ty sigma transcription after pheromone treatment and in different genetic backgrounds will be studied. Deletions from each end of Ty sigma will be used to sequence the element and then to create scanning mutations in order to define regions which are involved in regulating expression and determine whether they mediate positive or negative effects. 2. Identification of interactions which occur between the tRNA gene and Ty sigma. The effect of Ty sigma insertion on tRNA gene expression will be followed by measuring expression of the SUP2 tRNATyr gene associated with various recombinant configurations of Ty sigma. Expression of Ty sigma associated with transcriptionally active and inactive SUP2 genes will be determined. 3. Development of assay for Ty sigma transposition. Ty sigma will be over expressed and transposition into the genome or into a plasmid-borne tRNA gene target will be anlyzed. The roles that tRNA gene structural sequences and tRNA gene transcription play in position specificity can then be determined. The association between Ty sigma and tRNA genes offers a unique opportunity to extend the observations on regulatory interactions of transposable elements and nearby genes to a new class of genes and potentially different kinds of regulation. The position specificity of Ty sigma further suggests that these studies can make unique contributions to our understanding of retrotransposon integration mechanisms.