在bp +5位点可以发生从中止转录到有效转录的转变。pol iii转录基因的主要转录本很短，90 ~ 120元的tRNA基因和5 sRNA(占绝大多数的产品),甚至最长的记录(如信号识别颗粒)的RNA只有~ 500元。特殊功能的转录起始的存在因素束缚在转录单位-内TFIIIA类1基因(NH部分)and TFIIIC in class 1 and class 2 genes. Transcript elongation, which has been analyzed at single-step resolution on a single sc tRNA gene, is rapid with highly purified components (TFIIIC, TFIIIB and pol III), and also in crude extracts (Matsuzaki et al., 1994; Shaaban et al., 1996). In particular, TFIIIC does not present a barrier to transcript elongation, generating a delay at only a single site of only 0.15-0.2 s duration at 20C. In other words, the requirement to displace TFIIIC during transcript elongation is not rate-limiting for tRNA gene activity. On the other hand, transcript elongation slows down when short U-tracts, e.g. UUU, are laid down, even at high concentrations of NTPs. These pauses exceed the TFIIIC-imposed delay on transcription of the sc SUP4 gene by a factor of ~3 or greater.

Sc TFIIIC在体外的多个转录周期中完全从tRNA基因中转移(Bardeleben et al.， 1994)，在活跃的细胞生长过程中，其pol III基因在体内的占用率也很低(Roberts et al.， 2003)。