Transfer and 5S ribosomal RNA transcription

Control elements that, interact with TFIIIA 

The 5 sequence is not essential for accurate transcription initiation. When the region extending from the 5 end of the gene (that is, the part that would normally be considered to be the promoter) is deleted, RNA synthesis is carried out just as efficiently as on the native gene. The new 5 end of the transcript is complementary to whatever sequences take the place of the natural ones. Furthermore, initiation is only affected when sequences within the 5S rRNAgene are disrupted. The molecular explanation for this phenomenon is as follows  

A protein factor binds to the 5S rRNA gene. Binding is at the internal sequence that is required for accurate initiation. 

The bound factor then interacts with RNA polymerase III, which is then capable of initiation. During transcription, the multiple protein factors (called TFIIIs) remain bound to the transcribing gene. 

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