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I am trying to gain insight in the transcriptional regulation of a few genes, but I am unsure what is meant with cis-regulatory elements and how they are different from trans-regulatory elements?
RNA polymerase II mainly transcribes protein-encoding genes, and the transcriptional activity of many
of those genes is tightly regulated. Two cooperating components are key in regulating RNAP II
transcription. One component acts in cis and requires an element that is located on the same DNA
molecule as the transcribed gene, the so-called cis-regulatory DNA elements. The other component
acts in trans, i.e. it requires molecules separate from the gene containing DNA molecule, here referred
to as trans-acting factors.
Despite the fact that cis-regulatory DNA elements have different functional definitions, there
are two features that they have in common: they can be detected as DNase I hypersensitive sites
(HSs) in vivo and they are relatively small DNA fragments (200-300bp) that contain multiple binding
sites for certain trans-acting factors and their interacting partners. Trans-acting factors are a diverse
group of proteins (and RNA), which includes sequence-specific transcription factors, components of
the general transcription machinery, and co-factors. Many trans-acting factors can interact and as
such influence each other activities.