Tchénio T, Segal-Bendirdjian E, Heidmann T
Unités de Biochimie-Enzymologie et de Physicochimie Macromoléculaire, CNRS U147, Institut Gustave Roussy, Villejuif, France.
EMBO J. 1993 Apr;12(4):1487-97. doi: 10.1002/j.1460-2075.1993.tb05792.x.
Using as a reporter gene a non-coding proviral structure marked with an intron-containing indicator, we demonstrate the de novo formation, via a retrotransposition pathway, of canonical processed pseudogenes in cultured mammalian cells. Their structural features include endings corresponding to the start and termination of the RNA intermediate, intron loss, acquisition of a 3' poly(A) tail, and target site duplications of variable length. The absence of extracellular intermediates for these processes, and the elimination during retrotransposition of sequences in the reporter gene essential in cis for a retroviral cycle, further suggest that endogenous retroviruses or related elements are not involved. Pseudogene formation frequency is markedly increased (up to 10-fold) by several treatments including treatment with 5-azacytidine or tetradecanoyl phorbol acetate, or serum starvation, which do not act at the reporter gene transcription level, but rather on endogenous genes--including the LINE elements--necessarily involved in trans-complementation for retrotransposition.
我们使用一个带有含内含子指示标记的非编码前病毒结构作为报告基因，证明了在培养的哺乳动物细胞中，通过逆转座途径从头形成了典型的加工假基因。它们的结构特征包括与RNA中间体的起始和终止相对应的末端、内含子丢失、获得3'聚腺苷酸尾巴以及可变长度的靶位点重复。这些过程不存在细胞外中间体，并且在逆转座过程中报告基因中对逆转录病毒周期顺式必需的序列被消除，这进一步表明内源性逆转录病毒或相关元件不参与其中。几种处理（包括用5-氮杂胞苷或十四酰佛波醇乙酸酯处理、血清饥饿）可使假基因形成频率显著增加（高达10倍），这些处理并非作用于报告基因的转录水平，而是作用于内源性基因（包括LINE元件），这些基因对于逆转座的反式互补是必需的。
