Elfring L K, Axton J M, Fenger D D, Page A W, Carminati J L, Orr-Weaver T L
Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA.
Mol Biol Cell. 1997 Apr;8(4):583-93. doi: 10.1091/mbc.8.4.583.
Unfertilized eggs and fertilized embryos from Drosophila mothers mutant for the plutonium (plu) gene contain giant polyploid nuclei resulting from unregulated S-phase. The PLU protein, a 19-kDa ankyrin repeat protein, is present in oocytes and early embryos but is not detectable after the completion of the initial rapid S-M cycles of the embryo. The persistence of the protein during the early embryonic divisions is consistent with a direct role in linking S-phase and M-phase. When ectopically expressed in the eye disc, PLU did not perturb the cell cycle, suggesting that PLU regulates S-phase only in early embryonic development. The pan gu (png) and giant nuclei (gnu) genes also affect the S-phase in the unfertilized egg and early embryo. We show that functional png is needed for the presence of PLU protein. By analyzing png mutations of differing severity, we find that the extent of the png mutant phenotype inversely reflects the level of PLU protein. Our data suggest that PLU protein is required at the time of egg activation and the completion of meiosis.
来自钚（plu）基因突变的果蝇母体的未受精卵和受精卵胚胎含有由于S期不受调控而产生的巨大多倍体细胞核。PLU蛋白是一种19 kDa的锚蛋白重复序列蛋白，存在于卵母细胞和早期胚胎中，但在胚胎最初的快速S-M周期完成后就检测不到了。该蛋白在早期胚胎分裂过程中的持续存在与它在连接S期和M期方面的直接作用是一致的。当PLU在眼盘中异位表达时，它不会干扰细胞周期，这表明PLU仅在早期胚胎发育中调节S期。泛古（png）和巨核（gnu）基因也会影响未受精卵和早期胚胎中的S期。我们发现功能性的png是PLU蛋白存在所必需的。通过分析不同严重程度的png突变，我们发现png突变体表型的程度与PLU蛋白的水平呈反比。我们的数据表明，在卵子激活和减数分裂完成时需要PLU蛋白。
