Ronsseray S, Lehmann M, Nouaud D, Anxolabéhère D
Département Dynamique du Génome et Evolution, Institut Jacques Monod, UMR9922 CNRS-Université Denis Diderot, Paris, France.
Genetica. 1997;100(1-3):95-107.
In Drosophila melanogaster, crossing males carrying autonomous P elements with females devoid of P copies results in hybrid dysgenesis in the germline of progeny. The reciprocal cross produces non-dysgenic progeny due to a maternally inherited state non-permissive for P transposition. The capacity of a P copy to repress transposition depends on both its structure and its chromosomal location. Naturally occurring regulatory P elements inserted at the telomere of the X chromosome have been genetically isolated in a genomic context devoid of other P elements. One or two copies of autonomous P elements at this site (1A) are sufficient to elicit a strong P repression in the germline. These elements are flanked by Telomeric Associated Sequences, previously identified and described by Karpen and Spradling (1992) as having heterochromatic properties. The regulatory properties of P elements at 1A are strongly impaired by mutations affecting Su(var)205, which encodes Heterochromatin Protein 1, a non-histone heterochromatin protein. The regulatory properties of classical P strains are not sensitive to Su(var)205. Models based on chromatin structure or on nuclear localisation of the telomeres are discussed in order to explain both the strong regulatory properties of P elements at the X chromosome telomere and their sensitivity to Su(var)205.
在黑腹果蝇中，将携带自主P元件的雄性与不含P拷贝的雌性杂交，会导致后代生殖系中的杂种不育。由于母系遗传状态不允许P转座，反交产生的后代不会出现杂种不育。P拷贝抑制转座的能力取决于其结构和染色体位置。在没有其他P元件的基因组背景下，已通过遗传学方法分离出自然存在的插入X染色体端粒的调控性P元件。在此位点（1A）有一两个自主P元件拷贝就足以在生殖系中引发强烈的P抑制。这些元件两侧是端粒相关序列，Karpen和Spradling（1992年）先前已鉴定并描述其具有异染色质特性。影响Su(var)205的突变会严重损害1A位点P元件的调控特性，Su(var)205编码异染色质蛋白1，一种非组蛋白异染色质蛋白。经典P品系的调控特性对Su(var)205不敏感。文中讨论了基于染色质结构或端粒核定位的模型，以解释X染色体端粒处P元件的强调控特性及其对Su(var)205的敏感性。
