Ronsseray S, Lehmann M, Nouaud D, Anxolabéhère D
Département Dynamique du Génome et Evolution, Institut Jacques Monod, CNRS-Université Denis Diderot, Paris, France.
Genetics. 1996 Aug;143(4):1663-74. doi: 10.1093/genetics/143.4.1663.
Genetic recombination was used in Drosophila melanogaster to isolate P elements, inserted at the telomeres of X chromosomes (cytological site IA) from natural populations, in a genetic background devoid of other P elements. We show that complete maternally inherited P repression in the germline (P cytotype) can be elicited by only two autonomous P elements at 1A and that a single element at this site has partial regulatory properties. The analysis of the surrounding chromosomal regions of the P elements at 1A shows that in all cases these elements are flanked by Telomeric Associated Sequences, tandemly repetitive noncoding sequences that have properties of heterochromatin. In addition, we show that the regulatory properties of P elements at 1A can be inhibited by some of the mutant alleles of the Su(var)205 gene and by a deficiency of this gene. However, the regulatory properties of reference P strains (Harwich and Texas 007) are not impaired by Su(var)205 mutations. Su(var)205 encodes Heterochromatin Protein 1 (HP1). These results suggest that the HP1 dosage effect on the P element properties is site-dependent and could involve the structure of the chromatin.
利用遗传重组技术，在果蝇中从自然种群中分离出插入X染色体端粒（细胞学位点1A）的P因子，该遗传背景不含其他P因子。我们发现，仅两个位于1A位点的自主P因子就能在生殖系中引发完全母系遗传的P抑制（P细胞型），且该位点的单个P因子具有部分调控特性。对1A位点P因子周围染色体区域的分析表明，在所有情况下，这些因子两侧均为端粒相关序列，即具有异染色质特性的串联重复非编码序列。此外，我们发现1A位点P因子的调控特性可被Su(var)205基因的一些突变等位基因以及该基因的一个缺失所抑制。然而，参考P品系（哈维奇和德克萨斯007）的调控特性不受Su(var)205突变的影响。Su(var)205编码异染色质蛋白1（HP1）。这些结果表明，HP1对P因子特性的剂量效应具有位点依赖性，可能涉及染色质结构。
