Janetopoulos C, Cole E, Smothers J F, Allis C D, Aufderheide K J
Department of Biology, Texas A&M University, College Station, TX 77843, USA.
J Cell Sci. 1999 Apr;112 ( Pt 7):1003-11. doi: 10.1242/jcs.112.7.1003.
A unique structure, the conjusome, has been identified and initially characterized in Tetrahymena thermophila. The conjusome appears only during a specific phase of conjugation. Immunofluorescence microscopy reveals that the conjusome is strongly labeled by antibodies to the protein Pdd1p. Pdd1p is a chromodomain protein and participates in the formation of chromatin-containing structures in developing macronuclear anlagen. Recent studies suggest that Pdd1p is physically associated with the elimination of specific germ-line sequences from developing macronuclei (anlagen) and may play a role in heterochromatin assembly. The conjusome contains Pdd1p, but it is devoid of any detectable DNA. The conjusome appears before DNA elimination begins in the developing anlagen and after Pdd1p is found in the parental macronucleus. Transmission electron microscopic observations reveal that the conjusome is not a membrane-bounded structure. The conjusome ranges in size from about 1 microm to sizes approaching 7 microm, depending on its maturity. It is composed of a coarse reticulum of a fibrous, electron dense material, interspersed with apparent background cytoplasm. Our initial characterization does suggest a number of possible functions for what may be a new, transient organelle.
一种独特的结构——接合体，已在嗜热四膜虫中被鉴定并初步表征。接合体仅在接合的特定阶段出现。免疫荧光显微镜检查显示，接合体被针对蛋白质Pdd1p的抗体强烈标记。Pdd1p是一种色域蛋白，参与发育中的大核原基中含染色质结构的形成。最近的研究表明，Pdd1p与从发育中的大核（原基）中消除特定种系序列在物理上相关联，并且可能在异染色质组装中起作用。接合体含有Pdd1p，但没有任何可检测到的DNA。接合体在发育中的原基中DNA消除开始之前出现，且在亲代大核中发现Pdd1p之后出现。透射电子显微镜观察显示，接合体不是膜结合结构。接合体的大小范围从约1微米到接近7微米，这取决于其成熟度。它由一种纤维状、电子致密物质的粗网组成，其间散布着明显的背景细胞质。我们的初步表征确实为这个可能是新的、短暂存在的细胞器提出了许多可能的功能。
