Question

How does histone acetylation stimulate transcription initiation?

1) By loosening the chromatin structure and allowing access to the DNA
2) By promoting the binding of transcription factors to the DNA
3) By enhancing the activity of RNA polymerase
4) By inhibiting the binding of repressor proteins to the DNA

Answer 1

Histone acetylation facilitates transcription initiation by loosening the chromatin structure, enabling transcription factors to bind more easily and RNA polymerase to access the DNA.

Step-by-step explanation:

Histone acetylation stimulates transcription initiation primarily by loosening the chromatin structure, which allows greater access to DNA. This modification is performed by enzymes called histone acetyltransferases (HAT enzymes), which add acetyl groups to histones, reducing the positive charge on the histones and thereby decreasing the tightness of the DNA-histone interaction. As the chromatin becomes more open, it facilitates the binding of transcription factors to DNA, making it easier for RNA polymerase to access the DNA and initiate transcription.