Alternative isoforms of RNA polymerase III impact the non-coding RNA transcriptome, viability, proliferation and differentiation of prostate cancer cells

Jodie Malcolm, Bob White

Research output: Contribution to journalReview articlepeer-review


RNA polymerase III (pol III) synthesizes short noncoding RNA (ncRNA) exclusively and is unique in having
alternative paralogues of one of its subunits, POLR3G and POLR3GL. Although most pol III target loci can be
transcribed by either isoform, exceptions have been found. For example, depletion of POLR3G curtails the
production of BC200 and snaR ncRNAs that are implicated in cancer progression. Furthermore, POLR3G may
protect pol III against repression by MAF1, a key physiological regulator. Expression of POLR3G is promoted
selectively by MYC, NANOG and OCT4A, master regulators of stem cell pluripotency, resulting in its preferential
accumulation in undifferentiated cells. Indeed, differentiation of prostate cancer cells is suppressed by a positive
feedback mechanism between POLR3G and NANOG, involving the control of NANOG mRNA degradation by
ncRNAs. Specific knockdown of POLR3G inhibits proliferation and induces differentiation of prostate cancer cells,
but this response is not seen following comparable depletion of its POLR3GL paralogue. ML-60218 is a cellpermeable small molecule pol III inhibitor that triggers the replacement of POLR3G with POLR3GL. Proliferation
and viability of primary prostate cancer cells are suppressed by ML-60218, whereas differentiation is induced,
effects that mimic POLR3G depletion. Transient exposure to ML-60218 reduced tumour initiating activity in a
xenograft model. Untransformed prostate cells are much less sensitive to these treatments, raising the possibility
of therapeutic benefit.
Original languageEnglish
Pages (from-to)126-133
Number of pages8
JournalJournal of translational genetics and genomics
Publication statusPublished - 17 Feb 2022

Bibliographical note

© The Author(s) 2022


  • Prostate cancer
  • POLR3G
  • SINEs
  • RNA Polymerase III
  • MAF1
  • ncRNA

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