Question

Cells can control gene expression at many different levels.  Describe two different ways a cell could produce large amounts of a specific protein.

Answer 1

Cells can control gene expression at many different levels, like genetic level. Cells can modulate the protein synthesis at the genetic level via operon system. In prokaryotic cells Operon is a strech of DNA that consists of promoter region, operator region, and structural genes. Each structural genes can produce specific type of proteins. RNA polymerase binds in the promoter region (upstream of operator region) for the initiation of the transcription. In the DNA strand there is regulatory sequence called regulator gene, that can regulate the gene expression. Lactose is a inducer molecule for the production of large amount of protein from those structural genes. Lactose molecules binds with the repressor molecule and induces the protein synthesis in the prokaryotic cells.

In eukaryotic cell the enhancement of specific protein synthesis is occured by chromatin remodelling mechanism. This mechanism is classified into two classes, one is acetylation of histones in the chromosome and another is nucleosome remodelling.

i)Histone acetylation: Chromosone is packed into the histones. The promoter region of the DNA is wrapped in the histones. The enzyme histone acetyl transferase (HATs) acetylates the lysine residue in the histones. This acetylation causes the more accessability to the promoter region for RNA polymerase and others transcription proteins. This acetylation in the histones opens the chromosome structure so that RNA polymerase can easily bind with the promoter region and produce large amount specific protein in the eukaryotic cell.

ii) Nucleosome remodelling: This is a class of chromatin remodeler. Chromatin remodelling complex remodel the chromatin by using energy from ATP hydrolysis. This attachement of chromatin remodelling complex makes the promoter region more accessible to the RNA polymerase. This accessability of promoter region enhance the transcription process . So that mRNA synthesis will be enhanced, and subsequently protein synthesis will also be increased from that specific mRNA.

So prokaryotic and eukaryotic cells can control their gene expression at many different levels. By modulating gene expression cells can produce large amount of specific protein as the requirements. Histone acetylation and chromatin remodeling are the two different ways by which human body can produce large amount of protein from mRNA.