Question

4) Eukaryotic genes require the compact chromatin fibers to uncoil for DNA to be accessed by RNA polymerase. This chromatin remodeling is mediated by cis-acting elements and trans-acting factors. Describe the difference and name the two key players (one cis and one trans) that help to form the pre-initiation complex.

Answer 1

Difference between cis acting sequences and trans acting factors.

1. cis acting elements are generally noncoding DNA sequences that regulate transcription, whereas trans acitng elements are DNA coding sequences which code for proteins that will regulate transcription.
2. cis acting means acting on the same side and trans-acting means acting from different molecule.This means that cis acting elements genes are present on the same side as the gene to be transcribed and trans acting elements genes will be present on different location but will act on the site of the gene to be transcribed.Eg, the trans acting elements genes may be present on chromosome gene 11 but it will regulate the gene which is present on chromosome 9.
3. cis acting elements are generally promotors, enhancer which allow the transcription factors to bing and form preinitiation complex and trans acting elements coded proteins will be these factors and regulate them.

the two players that help form preinitiation complex are TATA box(cis acting) and TFIID (trans acting).