RNA Polymerase

RNA polymerases are composed of two groups; DNA-directed RNA polymerases EC (RNAP or RNApol, commonly referred to just as RNA polymerase), which are enzymes that catalyze the synthesis of an RNA chain from a DNA template; and RNA-dependent RNA polymerases EC (RdRp), which catalyze the synthesis of an RNA chain from an RNA template.

Gene Data

RNA Polymerase Inhibitors

Cat. No. Product Name / Activity
1229 Actinomycin D
Inhibits RNA polymerase
4025 α-Amanitin
Inhibitor of RNA polymerase II
5417 BMH 21
RNA polymerase I inhibitor; also p53 pathway activator
6974 BMS 986094
Inhibitor of HCV RNA-dependent RNA polymerase (RdRP; NS5b); potent hepatitis C virus (HCV) replication inhibitor
7231 EIDD 1931
Viral RNA-dependent RNA polymerase (RdRP) inhibitor; broad spectrum antiviral nucleoside
7225 Favipiravir
Viral RNA polymerase inhibitor
7229 Galidesivir dihydrochloride
Viral RNA-dependent RNA polymerase (RdRP) inhibitor; broad spectrum antiviral
7227 GS 441524
Viral RNA-dependent RNA polymerase (RdRP) inhibitor; broad spectrum antiviral nucleotide
1489 Mithramycin A
Inhibitor of DNA and RNA polymerase
7226 Remdesivir
Viral RNA-dependent RNA polymerase (RdRP) inhibitor; broad spectrum antiviral nucleotide prodrug


Cat. No. Product Name / Activity
7342 Emetine dihydrochloride
RNA polymerase inhibitor; inhibits replication of a broad range of RNA and DNA viruses, including SARS-CoV-2 and Zika
7586 Molnupiravir
Prodrug of antiviral nucleoside analog; inhibits SARS-CoV, SARS-CoV-2 and MERS-CoV infection
IKBKAP pre-mRNA splicing modulator
4501 Ribavirin
Antiviral guanosine ribonucleoside analog; misincorporated into mRNA by viral RNA polymerases
3253 Triptolide
Inhibits RNAPII-mediated transcription; antitumor, anti-inflammatory and immunosuppressive

RNA Polymerases Classification

In eukaryotes, there are four forms of RNA polymerase (I-IV), which are classified on the basis of the type of RNA they produce. RNA polymerase I (Pol I) makes a pre-ribosomal RNA (pre-rRNA 45S), which makes up ~50% of the RNA produced in a cell; RNA polymerase II (Pol II), which makes precursors of mRNAs, most snRNA and microRNAs; RNA polymerase III (Pol III), which makes tRNAs and rRNA 5S, as well as other small RNAs found in the cell. RNA polymerase IV is an enzyme, which makes small interfering RNA (siRNA) in plants.

Both bacteria and archaea each have only one type of RNA polymerase that is structurally similar to eukaryotic RNA polymerases. However, viruses employ different types of DNA-directed RNA polymerases, as well as RNA-dependent RNA polymerases (RdRp).

Transcription and RNA Types

During transcription, DNA-directed RNA polymerases direct the synthesis of an RNA chain complementary to the DNA template, by binding to a promoter sequence and initiating separation of the DNA double helix. Complementary ribonucleotide purine bases, adenine and guanine, and pyrimidine bases cytosine and uracil, bind and form the RNA chain, until a termination signal is reached.

DNA-directed RNA polymerases catalyze the production of either coding messenger RNA (mRNA), which become proteins, or non-coding RNA, sometimes called "RNA genes". There are four types of non-coding RNA:

  • transfer RNA (tRNA) - adds amino acids to polypeptide chains in the ribosomal site of protein synthesis during the translation step of protein synthesis
  • ribosomal RNA (rRNA) - incorporated into the ribosome
  • micro RNA (miRNA) - involved in regulating gene activity
  • catalytic RNA (ribozyme) - an RNA molecule that has catalytic abilities

DNA-directed RNA polymerase activity is tightly controlled throughout the initiation, elongation and termination phases of transcription by diverse regulatory signals ranging from protein factors to small molecule inhibitors. Newly transcribed RNA strands undergo post-transcriptional processing before leaving the nucleus. In contrast to DNA-directed RNA polymerases, RNA-dependent RNA polymerases catalyzes the direct replication of RNA, which produces an identical copy of RNA from an RNA template.

Role of RNA Polymerase in Epigenetics

DNA-directed RNA polymerase activity is a crucial requirement for the realization of epigenetic modifications, since it reads and translates both genetic and epigenetic information. An example of this is during X chromosome inactivation in females, whereby the RNA 'Xist' binds to and spreads out along the entire length of one of the two X chromosomes, blocking the access of the RNA polymerase and other transcription machinery. This prevention of transcription is key in regulating expression of genes located on the X chromosome.

RNA-dependent RNA Polymerase Inhibitors as Antivirals

RNA-dependent RNA polymerase (RdRP) inhibitors, such as the nucleoside analogs Favipiravir (Cat.no. 7225) and Remdesivir (Cat. no. 7226), have been developed as antivirals. Remdesivir is a prodrug of an adenosine nucleotide analog, which was originally developed in the efforts against the ebola virus disease and marburg virus infections. Favipiravir, a prodrug of a guanosine nucleotide analog, also inhibits RNA-dependent RNA polymerases. The ability of these inhibitors to inhibit viral replication has resulted in their also being evaluated as a treatment for SARS-CoV-2 infection, the virus responsible for the COVID-19 pandemic.

RNA Polymerase Gene Data

Gene Species Gene Symbol Gene Accession No. Protein Accession No.
POLR1A Human POLR1A NM_015425 O95602
Mouse Polr1a NM_009088 O35134
Rat Polr1a NM_031772 O54889
POLR1B Human POLR1B NM_019014 Q9H9Y6
Mouse Polr1b NM_009086 P70700
Rat Polr1b NM_031773 O54888
POLR1C Human POLR1C NM_004875 O15160
Mouse Polr1c NM_009085 P52432
Rat Polr1c NM_001008330 Q5RJK9
POLR1D Human POLR1D NM_015972 Q9Y2S0
Mouse Polr1d NM_181730 P97304
POLR1E Human POLR1E NM_022490 Q9GZS1
Mouse Polr1e NM_022811 Q8K202
Rat Polr1e NM_001107938 XP_233004
POLR2A Human POLR2A NM_000937 P24928
Mouse Polr2a NM_009089 P08775
Rat Polr2a XM_343922 XP_343923
POLR2B Human POLR2B NM_000938 P30876
Mouse Polr2b NM_153798 Q8CFI7
Rat Polr2b NM_001106002 XP_214021
POLR2C Human POLR2C NM_032940 P19387
Mouse Polr2c NM_009090 P97760
Rat Polr2c NM_001012473 Q5EB90
POLR2D Human POLR2D NM_004805 O15514
Mouse Polr2d NM_027101 Q9D7M8
Rat Polr2d NM_001108886 XP_344660
POLR2E Human POLR2E NM_002695 P19388
Mouse Polr2e NM_025554 Q80UW8
Rat Polr2e NM_001109614 XP_001076333
POLR2F Human POLR2F NM_021974 P61218
Mouse Polr2f NM_027231 P61219
Rat Polr2f NM_031335 O88828
POLR2G Human POLR2G NM_002696 P62487
Mouse Polr2g NM_026329 P62488
Rat Polr2g NM_053948 P62489
POLR2H Human POLR2H NM_006232 P52434
Mouse Polr2h NM_145632 Q923G2
Rat Polr2h NM_001134789 Q9Z0W2
POLR2I Human POL2I NM_006233 P36954
Mouse Polr2i NM_027259 P60898
Rat Polr2i NM_001106244 XP_214895
POLR2J Human POLR2J NM_006234 P52435
Mouse Polr2j NM_011293 O08740
Rat Polr2j NM_001105921 XP_213753
POLR2K Human POLR2K NM_005034 P53803
Mouse Polr2k NM_001039368 Q63871
Rat Polr2k XM_219604 XP_219604
POLR2L Human POLR2L NM_021128 P62875
Mouse Polr2l NM_025593 P62876
Rat Polr2l NM_001143911 Q7TPA2
POLR3A Human POLR3A NM_007055 O14802
Mouse Polr3a NM_001081247 NP_001074716
Rat Polr3a XM_341388 Q5RK26
POLR3B Human POLR3B NM_018082 Q9NW08
Mouse Polr3b NM_027423 P59470
Rat Polr3b XM_343188 XP_343189
POLR3C Human POLR3C NM_006468 Q9BUI4
Mouse Polr3c NM_028925 Q9D483
Rat Polr3c NM_001012081 Q5XIL3
POLR3D Human POLR3D NM_001722 P05423
Mouse Polr3d NM_025945 Q91WD1
Rat Polr3d NM_001031653 Q4FZS9
POLR3E Human POLR3E NM_018119 Q9NVU0
Mouse Polr3e NM_025298 Q9CZT4
Rat Polr3e NM_001108503 XP_341920
POLR3F Human POLR3F NM_006466 Q9H1D9
Mouse Polr3f NM_029763 Q921X6
Rat Polr3f NM_001107784 XP_230642
POLR3G Human POLR3G NM_006467 O15318
Mouse Polr3g NM_001081176 Q6NXY9
Rat Polr3g NM_001109468 XP_001061237
POLR3H Human POLR3H NM_138338 Q9Y535
Mouse Polr3h NM_030229 Q9D2C6
Rat Polr3h NM_001127295 XP_216998
POLR3K Human POLR3K NM_016310 Q9Y2Y1
Mouse Polr3k NM_025901 Q9CQZ7
Rat Polr3k NM_001014259 Q5FVH1