Respuesta :
Answer:
The correct answer is histone proteins must be present in the promoter.
Explanation:
Transcription factors act as regulatory proteins or DNA binding proteins which interract with promoter region of a DNA molecule during transciption.
Transcription factor can both upregulate and downregulate the expression of the target DNA to which it interact .
Transcription factors use various processes to regulate gene expression
a Histone Acetylation An enzyme histone Acetyl transferase catalyses the acetylation of epsilon -NH2 group of positively charged lysine residue of histone proteins present in the target DNA.The acetylation result in weakening the interaction between DNA and Histone protein.As a result the target DNA is very much free to undergo transcription thus up regulating the gene expression.
b Histone deacetylation An enzyme histone deacetylase catalyses the removal of additional acetyl group from the acetylated lysine residue of histone protein present in target DNA.As a result the target DNA gets less freedom to carry out transcription thus decreasing or down regulating the gene expression.
