PROSITE documentation PDOC00106
Eukaryotic RNA polymerase II heptapeptide repeat


RNA polymerase II (EC [1,2] is one of the three forms of RNA polymerase that exist in eukaryotic nuclei. The C-terminal region of the largest subunit of this oligomeric enzyme consists of the tandem repeat of a conserved heptapeptide [3]. The number of repeats varies according to the species (for example: 17 in Plasmodium, 26 in yeast, 44 in Drosophila, and 52 in mammals). The region containing these repeats is essential to the function of polymerase II. This repeated heptapeptide (called CT7n or CTD) is rich in hydroxyl groups. It probably projects out of the globular catalytic domain and may interact with the acidic activator domains of transcriptional regulatory proteins. It is also known to bind by intercalation to DNA. RNA polymerase II is activated by phosphorylation. The serine and threonine residues in the CT7n repeats are the target of such phosphorylation.


The consensus for the heptapeptide repeat is Y-S-P-T-S-P-S, but we have allowed variants in position 2, 4, and, 7 of the pattern so as to detect some of the imperfect repeats.


Protozoan parasites such Trypanosoma and Crithidia do not have a CT7n domain.

Last update:

December 1991 / Text revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

RNA_POL_II_REPEAT, PS00115; Eukaryotic RNA polymerase II heptapeptide repeat  (PATTERN)


1AuthorsWoychik N.A. Young R.A.
TitleRNA polymerase II: subunit structure and function.
SourceTrends Biochem. Sci. 15:347-351(1990).
PubMed ID1700503

2AuthorsYoung R.A.
TitleRNA polymerase II.
SourceAnnu. Rev. Biochem. 60:689-715(1991).
PubMed ID1883205

3AuthorsCorden J.L.
TitleTails of RNA polymerase II.
SourceTrends Biochem. Sci. 15:383-387(1990).
PubMed ID2251729

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