The brownDominant (bwD) allele contains a large insertion of heterochromatin, which causes the locus to aberrantly associate with heterochromatin in interphase nuclei and silences the wild-type allele in heterozygotes. Transgenes placed near the bw+ locus, in trans to bwD, can also be silenced. The strength of silencing (called trans inactivation) varies with the regulatory sequences of the transgene and its distance away from the bwD insertion site in trans. In this study, we examine endogenous sequences in cis that influence susceptibility of a reporter gene to trans inactivation. Flanking deletions were induced in two parental lines containing P-element transgenes showing trans inactivation of the mini-white reporter. These new lines, which have mini-white under the influence of different endogenous sequence elements, now show varied ability to be silenced by bwD. Determination of the deleted regions and the levels of mini-white expression and trans inactivation has allowed us to explore the correlation between cis sequence elements and susceptibility to trans inactivation and to identify a 301-bp sequence that acts as an enhancer of trans inactivation. Intriguingly, this region encompasses the upstream regions of two divergently transcribed genes and contains a sequence motif that may bind BEAF, a protein involved in delimiting chromatin boundaries.
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机译：棕色 优势 （ bw D ）等位基因含有大量的异染色质插入物，这导致基因座与相间核中的异染色质异常缔合，并使杂合子中的野生型等位基因沉默。转基因位于 bw + 位点附近，位于 trans 到 bw 的位置 D 也可以被静音。沉默的强度（称为 trans 失活）随转基因的调控序列及其与 bw D < / sup>插入站点，位于 trans 中。在这项研究中，我们检查了 cis 中的内源序列，这些序列会影响报告基因对 trans 失活的敏感性。在两个含有P元素转基因的亲本系中诱导侧翼缺失，这两个亲本系显示 mini-white 报告基因的 trans 失活。这些新品系在不同的内源序列元素的影响下具有 mini-white ，现在显示出不同的被 bw D沉默的能力。 em> 。确定缺失区域以及白色表达和 trans 失活的水平使我们能够探索 cis 序列元件与易感性之间的相关性进行 trans 灭活，并鉴定一个301-bp序列，作为 trans 灭活的增强子。有趣的是，该区域涵盖了两个不同转录的基因的上游区域，并包含可与BEAF结合的序列基序，BEAF是一种涉及限定染色质边界的蛋白质。
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