摘要：

All RNA polymerase III transcribed genes are constructed according to a similar design, in which two important elements are recognized: (1) a region of DNA essential for promotion of transcription and directing initiation of transcription upstream from its 5' boundary (this could be considered the "promoter" of the gene); (2) a termination signal located at a variable distance downstream from the 3' boundary of the promoter region. In every RNA polymerase III transcribed gene the promoter sequence is always part of the transcript. The overall process of transcription, at least in the Xenopus oocyte system, is influenced by the sequences located outside the internal promoter. The structure of the internal promoter and its relationship with the initiation of transcription is different for tRNA and for 5 S RNA genes. Polymerase III transcribed genes are classified into two classes. Class I includes tRNA genes, VA I and VA I1 genes, EBER I and EBER II genes, and the Alu-family of interspersed repetitive sequences. Class 2 includes only 5 S RNA genes.

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