Cell growth- and differentiation-dependent regulation of RNA polymerase III transcription

Abstract

RNA polymerase III transcribes small untranslated RNAs that fulfill essential cellular functions in regulating transcription, RNA processing, translation and protein translocation. RNA polymerase III transcription activity is tightly regulated during the cell cycle and coupled to growth control mechanisms. Furthermore, there are reports of changes in RNA polymerase III transcription activity during cellular differentiation, including the discovery of a novel isoform of human RNA polymerase III that has been shown to be specifically expressed in undifferentiated human H1 embryonic stem cells. Here, we review major regulatory mechanisms of RNA polymerase III transcription during the cell cycle, cell growth and cell differentiation.

Figure 1

Mammalian RNA Polymerase III promoters and transcription factors. Promoter types 1–3. III A = TFIII A. TFIII B subunits are TBP, BDP1, BRF1 and BRF2; TFIIIC subunits are indicated as C35, C63, C90, C102, C110 and C220. PTFα, β, γ and δ subunits are also denoted according to the molecular weight of the respective SNAPc subunits (190, 50, 43 and 45). In addition, SNAP19 is shown, which has not been described in PTF. The ternary complexes composed of RPC39, RPC62 and RPC32α or RPC32β are high lightened within the symbolic representation of RNA polymerase III.

Figure 2

(A) Schematic representation of several regulatory pathways of mammalian RNA polymerase III transcription: Ras-dependent pathways. (B) Schematic representation of several regulatory pathways of mammalian RNA polymerase III transcription: Regulation of Pol III transcription by tumor suppressor and oncogene proteins.

Figure 3

Regulation of RNA polymerase III transcription during differentiation of mouse F9 embryonic carcinoma cells.

Figure 4

Regulation of RNA polymerase III transcription during differentiation of human H1 embryonic stem cells.