Fanti L, Dorer D R, Berloco M, Henikoff S, Pimpinelli S
Istituto di Genetica, Università di Bari, I-70126 Bari, Italy.
Chromosoma. 1998 Nov;107(5):286-92. doi: 10.1007/s004120050310.
Heterochromatin protein 1 (HP1) of Drosophila and its homologs in vertebrates are key components of constitutive heterochromatin. Here we provide cytological evidence for the presence of heterochromatin within a euchromatic chromosome arm by immunolocalization of HP1 to the site of a silenced transgene repeat array. The amount of HP1 associated with arrays in polytene chromosomes is correlated with the array size. Inverted transposons within an array or increased proximity of an array to blocks of naturally occurring heterochromatin may increase transgene silencing without increasing HP1 labeling. Less dense anti-HP1 labeling is found at transposon arrays in which there is no transgene silencing. The results indicate that HP1 targets the chromatin of transposon insertions and binds more densely at a site with repeated sequences susceptible to heterochromatin formation.
果蝇的异染色质蛋白1（HP1）及其在脊椎动物中的同源物是组成型异染色质的关键成分。在这里，我们通过将HP1免疫定位到沉默转基因重复阵列的位点，为常染色体臂内存在异染色质提供了细胞学证据。多线染色体中与阵列相关的HP1量与阵列大小相关。阵列内的反向转座子或阵列与天然存在的异染色质块的距离增加可能会增加转基因沉默，而不会增加HP1标记。在没有转基因沉默的转座子阵列中发现抗HP1标记密度较低。结果表明，HP1靶向转座子插入的染色质，并在具有易形成异染色质的重复序列的位点更密集地结合。
